ID: 1770

Название работы: MooTools Essentials The Official MooTools Reference for JavaScript and Ajax Development

Категория: Книга

Предметная область: Информатика, кибернетика и программирование

Описание: A Note on the Code Formatting in This Book. Why You Should Use a JavaScript Framework. Anonymous Methods vs. Named Functions. Adding and Removing Element Events. Writing Flexible Classes.

Язык: Английский

Дата добавления: 2012-11-11

Размер файла: 1.41 MB

Работу скачали: 24 чел.

About firstPress
Apress's firstPress series is your source for understanding cutting-edge technology. Short,
highly focused, and written by experts, Apress's firstPress books save you time and effort. They
contain the information you could get based on intensive research yourself or if you were to
attend a conference every other week—if only you had the time. They cover the concepts and
techniques that will keep you ahead of the technology curve. Apress's firstPress books are real
books, in your choice of electronic or print-on-demand format, with no rough edges even when
the technology itself is still rough. You can't afford to be without them.

MooTools Essentials: The Official MooTools Reference for
JavaScript™ and Ajax Development
Dear Reader,
Whether you are visiting or building a web site these days, you can’t deny that JavaScript has
become an important part of the experience. Visitors to web sites expect them to be interactive
and responsive, and that means that those of us who build them must spend the time to make
that experience come alive.
In the past, JavaScript was often a tedious business, with browsers each offering their own
mercurial blend of standard and nonstandard functionality. Modern JavaScript has taken off
with the advent of JavaScript frameworks: libraries that enhance the JavaScript language itself
and help you avoid all the pesky browser bugs.
MooTools is a JavaScript framework that enables you to write clean, concise, reusable code to
animate and dynamically change the content on your site using Ajax and other technologies,
taking care of all the grunt work for you. This book aims to make the process of getting started
with MooTools an easy one, covering everything from downloading the code and adding it to
your pages to explaining what each class and method does (and, perhaps more importantly,
when you’ll use each one).
I’ve combined real-world examples with nuanced explanations of everything you need to know
to make your site fun and engaging. You’ll be adding effects and Ajax in no time.
Have fun,
Aaron Newton

Preface
Acknowledgments
I feel compelled to quickly thank the people who helped out in one way or
another with the creation of this book. The MooTools development team
deserves thanks for writing the library—Valerio Proietti in particular for
starting and running the whole project and for helping out with the
technical editing of this book. Ditto for Harald Kirschner, who also helped
out with the technical editing.
I’d like to thank CNET, who basically paid me to learn all this stuff and
contribute to MooTools. I’d like to give mad props to the fine people at
Apress, especially my copy editor, Ami. Previously I would have always
said, “Whoever does QA for code I write are my favorite people because
they find my mistakes and make me look better.” I’m going to have to add
copy editors to that list as they make me seem like a far more learned man.
Finally I’d like to thank my patient, supportive, and humble wife who
insisted that I dedicate this book to her, which, of course, I do.
A Note on the Code Formatting in This Book
I’d like to take a moment to note that throughout the code examples in this
book, you’ll see some occassionally odd code layouts. The margins of the
book allow for only 56 characters per line before it wraps, and this
presented a lot of challenges. My intention in the layouts in these situations
was to format the code in a way that was most legible, not in a way that
illustrated how I actually format the code I write. I mention it here lest you
emulate the bizarre indentations you may encounter here.

MooTools Essentials
xi

Introduction
Over the past several years, JavaScript has undergone some serious
changes while simultaneously becoming more and more important to both
developers and users of the Web. By now, people just expect pages to be
interactive, and it’s up to you, the web developer, to meet those
expectations and, when possible, exceed them.
Say you went to a web site today and encountered an item—a video, a
story, a photo, a download—and next to that item’s title was a five-star
rating system with an invitation for you to click a star to rate it. Without
thinking about it, you’d expect to be able to click the star of your choice
and see the rating change. It might not surprise you if the page reloaded to
ask you to register or log in, but the next time you rated something, you’d
expect the rating to change to match your choice. But if every time you
clicked a star the whole page reloaded, you’d feel something was wrong.
Maybe you wouldn’t be able to put your finger on it (most users certainly
wouldn’t think JavaScript or Ajax might be behind the problem), but
something would feel odd.
The users who visit your site will have expectations that the site behave
like the others they go to, and if yours doesn’t, even if it looks great and
has awesome content, it’ll feel old. This might not drive people from using
your site, but it will certainly result in less usage of the features you
develop.
To meet these expectations, you’ll find that you can’t do it with the skill
sets traditionally required to build a web site. Back-end developers of Java,
Perl, PHP, Python, Ruby, and so forth often find writing JavaScript to be
tedious and fraught with frustration when dealing with the browser quirks,
while the people who spend most of their time working on the client side—
creating the design, HTML, CSS, and images—often don’t have a lot of
serious programming experience.

MooTools Essentials
xiii

Because the functionality that users increasingly expect is robust,
developers who actually know how to program find themselves working on
the client side. This means graphic designers must work closely with
engineers, who typically don’t think about interaction and interfaces.
JavaScript Frameworks
User expectations have driven application development, resulting in Ajax,
animation, drag and drop, and other UI concepts making their way into the
web browsing experience. Until a few years ago, accomplishing any of
these things in JavaScript was painful and unpleasant, and consequently
avoided. That all changed, though, with the introduction of JavaScript
frameworks.
The idea behind a JavaScript framework is that it will abstract all the code
you write from the engine that executes it. This helps developers overcome
the most frustrating part of working with JavaScript: the environment—the
browser—is one over which you as a developer have no control. Without
getting into the history of JavaScript and the various competing standards
that were implemented in each new generation of browsers, it is sufficient
to say that browsers don’t all behave the same way, which can also be said
of how they handle HTML and CSS.
Why You Should Use a JavaScript Framework
JavaScript frameworks help alleviate the problems I just mentioned and
bring a whole host of other benefits to the environment. Most notably,
JavaScript frameworks
Abstract your code from the runtime environment (the browser) so that
various environment quirks can be handled by the framework and new quirks
that are introduced subsequently can be managed in one place.
Create a foundation base of code on which you can build and grow.
xiv
MooTools Essentials

  Create a common environment for groups to contribute (with their own
extensions, plug-ins, and bug fixes).
  Encourage the use of similar patterns across disparate web sites so that users
can reuse the knowledge they learn (clicking five stars to rate something, for
example).
Of all the frameworks that hit the market in the last few years, Prototype.js
Released in 2005, it remains one of the most well-written and robust
frameworks, and it gained a great deal of acceptance and praise from
developers who were on the edge of client-side development.
Prototype.js did three things that made it an instant hit:
  It introduced concepts and shortcuts that became instant standards for
JavaScript development, making things like Ajax and DOM selection easy to
do.
  It extended native objects like Strings, Arrays, and Functions (but not
Elements) to add functionality that wasn’t built into JavaScript already.
  It showed people that this kind of thing was even possible.
Of all the contributions that Prototype.js offered (and continues to offer;
it’s still very much supported and in development), it’s that last item that
was, from my perspective, the most important gift. It showed developers
that writing a framework that made JavaScript itself better and easier and
even kind of fun was possible.
About MooTools
This book is about MooTools, a JavaScript framework, primarily authored
by Valerio Proietti, that gets some of its original inspiration from
Prototype.js as well as from other sources (most notably Dean Edwards’
Base library). Originally, MooTools began when Valerio released an add-
on to Prototype.js called Moo.fx (which is still available at

MooTools Essentials
  xv

(3KB!) effects library that was quite popular for both its ease of use and its
small size.
Not content to just release an add-on for Prototype, Valerio began work on
his own framework, MooTools (which stands for My Object-Oriented
Tools), and released it in September 2006. The reason he started this task
was because Prototype.js, which added numerous shortcuts to the
prototypes of Array, String, Function, and so on, didn’t extend the
Element prototype, and he was tired of repeatedly typing the prototype’s
Element generic.
At its heart, MooTools is a JavaScript framework that provides those three
essential things that I mention earlier about Prototype.js: it provides
shortcuts and foundation classes that make doing common things easy, it
extends native objects to add functionality to them, and, perhaps most
importantly, the library itself serves as an illustration of how to write
JavaScript well, and, more specifically, how to write JavaScript using
MooTools.
These concepts aren’t necessarily unique to MooTools; indeed, nearly all
JavaScript frameworks (and there are a LOT of them) do these things to
varying degrees of success. What does make MooTools unique is its coding
style, its well-rounded offering, and its basic philosophical approach to its
continued development. The defining characteristics of MooTools are as
follows:
  Don’t duplicate code.
  Add functionality that fits in principle with JavaScript’s own design
philosophy.
  If there’s a good standard in place that works well but is not yet implemented,
implement the standard.
  Extend native objects (String, Function, Array, Element, Event, and
Number) as JavaScript was designed to do.
xvi
MooTools Essentials

  Write clean, clear, well-named code that is understandable when read by
anyone with the skills to understand it.
  Be careful not to demand too much of the browser (memory, CPU cycles,
etc.).
  Abstract as much away from the browser as possible.
  Whenever possible, make it still feel like you’re writing JavaScript.
  Make it easy. Make it fun. Make it inspiring.
  Make it modular.
MooTools vs. Other Frameworks
When people ask me which framework to choose, I can only give them my
opinion, which is that you really can’t go wrong with Dojo, Yahoo! User
Interface (YUI), Prototype, jQuery, or MooTools (there are others out
there, so this short list is by no means definitive). These frameworks are all
good choices. They all have their different focuses and approaches to
problems. Some have very different philosophies and styles, but ultimately
they are well written, efficient, and well supported.
MooTools and Prototype both believe strongly in altering the prototypes of
native elements (String, Array, Function, etc.—except Object, never
Object!) as well as offering numerous methods on these prototypes to help
you work with them. YUI, jQuery, and Dojo don’t do this. Both YUI and
jQuery are highly namespaced, which makes them ideal for environments
you don’t control completely (e.g., where there might be third-party
JavaScript, such as ads), while MooTools and Prototype won’t play nice
with other frameworks or environments that use function names like $() or
modify the native objects themselves. The only downsides to the
namespacing: in the case of YUI, the code is sometimes a little verbose,
and frameworks that maintain all their methods in a namespace will always
be slightly slower than methods added to native prototypes, although it’s
unlikely that this speed hit will be noticeable to you unless you are iterating

MooTools Essentials
  xvii

over a lot of objects. These things are not bad things—it’s just the way
these frameworks are.
The advantage to modifying the native elements (aside from a slight speed
advantage) is that you can add methods to these elements and extend their
functionality. It’s the difference between "hi".alert() and
alert("hi"). It’s subtle, but the former example is how JavaScript itself
works. The downside is that if you define a method (like, say,
Array.each), and something else in your environment (another script)
defines the same thing, one is overwritten. The upside is a more elegant
model for adding functionality to things (at least I think so).
Additionally, some frameworks focus on re-creating a somewhat traditional
inheritance model. MooTools focuses on this and highly encourages code
reuse and modular designs. All frameworks have methods to create
reusable code—I’m not saying they don’t. But this is the heart of
MooTools, and not all frameworks can make that claim. JavaScript has a
prototypal inheritance model (see “Prototypal Inheritance” in the
Appendix), and MooTools creates a structure to take advantage of this
model in a way that will be more familiar to developers used to languages
like Java.
MooTools also is designed in a modular fashion so that you don’t need all
of it to make a page work. If you only need Ajax, you can deliver less
JavaScript, and therefore fewer bytes.
If I were to sum up what makes MooTools special, it’s that it makes
JavaScript itself better. It focuses on the JavaScript programming language
and seeks to streamline it, but not deviate from the basic principles of what
makes JavaScript JavaScript. It’s not trying to look like CSS, and it’s not
trying to look like C++ or Java (although its class architecture is certainly
more similar to Java than traditional JavaScript in some ways). Other
frameworks do this, too (and here I’m thinking of Prototype.js). What
MooTools has that Prototype.js doesn’t (the last time I looked anyway) is a
xviii
MooTools Essentials

set of powerful animation routines and plug-ins (like sortable lists and drag
and drop). If you use Prototype.js and wish to have access to effects or drag
and drop, you must include both it and another library like script.aculo.us
or write this functionality yourself. Also, MooTools modular design takes
up a much smaller footprint than Prototype and script.aculo.us together.
I’ll reiterate that choosing any of these frameworks isn’t a bad thing to do.
Look at the strengths of the other options. Choose the one that suits your
needs and your design principles and offers the right mix of flexibility and
functionality.
About the Author
I’m a product manager by trade, but I started my career as an interface
designer in the early days of the Web. I’ve worked at numerous startups,
CNET hired me as a product manager for the development and launch of
Download.com Music. In late 2005, I started focusing on JavaScript for the
network, as it was always an interest of mine since my days doing interface
design in the mid-1990s. I began blogging on an internal blog for CNET,
trying to spread the knowledge I was aggregating. In February 2006, I
began publicly blogging on the topic at my blog, Clientside
At first, most of my effort was focused on Prototype.js, but when
MooTools launched its suite of code in late 2006, I quickly became a
convert and devoted my energy to it.
Why did I choose MooTools? A few reasons, many of which had to do
with CNET’s needs and some of which had to do with my own tastes. For
starters, I always admired how much power Valerio Proietti managed to
cram into Moo.fx. It was a 3KB effects library so cleanly written and
manicured that I marveled at its artistry. I learned a lot from that 3KB.

MooTools Essentials
xix

When MooTools launched, I quickly read through the source code and
learned more.
In addition to that was the modular design of the library. Prototype.js is a
relatively large library, and even with it in your environment you still
needed other libraries (like Moo.fx) to really make the most of it.
MooTools offered a modular design that let you choose which things you
needed for any given project.
Finally, MooTools was just more well rounded for the kind of work that we
at CNET were doing. CNET wasn’t in the business of authoring the next
webmail client to compete with Yahoo or Gmail. We had busy HTML
pages that we wanted to add some interaction to, and MooTools seemed to
be perfect for it.
After I made this decision, I immediately began contributing to the
MooTools project. I authored all the original documentation (at that time
there were no docs; but to be fair, almost none of the other frameworks had
comprehensive documentation either) and then the first comprehensive
foundation of this book and the reason that I was approached to author it.
Since I first started using it, MooTools has grown and matured
dramatically, and it offers much of the same functionality that Prototype.js
and other frameworks offer. What makes it remain my choice is the artistic
elegance of the code itself and the design aesthetic that shapes its
development. Simply put, MooTools makes writing JavaScript fun.
I do commit code, but it’s a rare occurrence these days. Instead, I tend to
author my own plug-ins and release those for others to use while
communicating with the development team frequently and offering
feedback to new features and changes. On occasion, something I write will
get consumed by MooTools.
xx
MooTools Essentials

This book is NOT for beginning programmers or for those with no
programming experience. Readers should be familiar with object-oriented
programming practices and ideally should have an understanding of
JavaScript’s prototypal inheritance model and functional programming
practices (also known as lambda), though these topics are reviewed in this
book’s appendix.
What You Need to Know
Readers should be familiar with the basic syntax of JavaScript as well as
the Document Object Model (DOM) presented by the browsers. Experience
with HTML and CSS is also obviously necessary.
Finally, you should be familiar with basic debugging practices for DOM
scripting. The excellent Firefox plug-in Firebug is a must-have for this
kind of development, so you should have experience using it or similar
applications for debugging.
If you aren’t familiar with these things, I suggest you check out
Accelerated DOM Scripting with Ajax, APIs, and Libraries by Jonathan
Snook et al. (Apress, 2007). I also recommend the following online
resources:

Summary
JavaScript has come a long way in the last few years, but so have user
expectations. Writing JavaScript has become more important and now
consumes an ever larger part of the resource pie, both in time spent to
create a web site and the bytes delivered to the browser.
Using a good JavaScript framework will help everyone who spends time on
your web site, whether they are making the site with you or visiting it.
JavaScript is a highly expressive and powerful language, and when you
have mastered it and can make full use of a framework like MooTools,
your visitors will notice. Once you get past the basics, you can start
imagining user experiences that are fun and fluid, and that’s the whole
point of putting in the time with something like MooTools.

MooTools Essentials
xxiii

Chapter 1: Getting Started with MooTools
In this chapter, I’ll cover some key steps and concepts that you should
understand before you start writing code with MooTools. For anyone
familiar with modern DOM scripting principles, most of this chapter can be
skimmed over, but if you’re new to this stuff, don’t miss out, as it’ll save
you some headaches.
Here I’ll cover the following:
  Downloading MooTools
  Using MooTools’ modular design
  Understanding compatibility issues for upgrading from one version to the
next
  Adding MooTools to your page(s) after you’ve downloaded it
  Coding for reuse
  Understanding concatenation and compression

You’ll get a page that looks like this:

Here you can download the MooTools core compressed or uncompressed. I
recommend using the uncompressed version for development and the
compressed version for your live site. I’ll cover some methods to compress
your own copy along with the code you write later in this chapter.
Downloading MooTools Official Plug-Ins
The Core download includes all the basic portions of the MooTools library
needed to author Ajax, effects, and your own classes as well as all the
extentions to the native objects (Element, Array, String, etc.). It does
not, however, include some of the additional functionality that is available
2
MooTools Essentials

from the official MooTools library. To get these add-ons, you’ll need to
click the More Builder link on the right of the download page. Doing so
will give you an interface where you can check off the additional plugins
you want and let you download them as a separate file:

Here you can download plug-ins that let you make elements draggable,
create accordion type controls or tooltips, and more. Just check off the
scripts you want and then select your compression and download it.

MooTools Essentials
3

Core Builder
You can also, if you choose, build your own custom library instead of
downloading the core file from the main download page. This can be useful
if you’re building, say, a mobile app and you just want some of the basic
functionality that MooTools has to offer. To build your own core, click the
Core Builder link on the right. You’ll get an interface just like the More
Builder with all the files that comprise the MooTools core. If you were to
select all these and download them, you would get a file that had the same
contents as the file listed in the first step earlier.
Don’t get overwhelmed by all the download options. I’ll cover them all in
the coming pages.
Making Use of MooTools’ Modular Design
MooTools is designed so that you can include only the JavaScript you need
for your page. Part of the MooTools code base is a dependency map that
allows this download page to fill in any gaps for what you need for your
application. If, for example, you need to use the Fx.Tween class, just click
the Fx.Tween.js option, and all the dependencies for that file are
automatically selected for you.
Tip
For development purposes, you might want to download the
whole library. I’ll stress that you shouldn’t launch your application like this;
it's really rare for an application to need everything MooTools has to offer.
However, if you want to get it all, it can get tedious to click everything on
the list, so here’s a shortcut: open Firebug and execute the following in the
console to check all the items for you to download:
Download.all()
4
MooTools Essentials

Compatibility
With each release of MooTools, there is a corresponding compatibility
script that will alias function and variable names to their counterparts in the
newer version. This adds more code to your environment, but not much,
and if you have a lot of code written for an earlier version, this can help
you transition to the newer release.
Note
When using MooTools, you should always reference only the
variables and methods outlined in the documentation. Though classes have
more methods and properties than are defined in the documentation, these
are considered private, and the compatibility scripts that accompany each
release maintain only the public methods and properties. All the others are
considered private, so if you reference them in your own code, you’ll have
issues when you upgrade.
Compression Options
MooTools provides several options for compressing the code it delivers to
you when you download it. Compressing the code doesn’t change the way
you use it, but rather removes all the extra spaces and transforms inner
variable names to save space. The result is a much smaller file than one
with all the indentation and line breaks.
The compression options you have with your download are
  YUI Compressor: This compressor is the most efficient and is what you
should use when you’re ready to release your code.
  No Compression: The source code is delivered unaltered.
For development, I recommend turning compression off entirely so that
you can easily debug any errors you encounter. If you use a compressed
version for development and get an error, the line number will always be
line #1, because compression removes all the line breaks.

MooTools Essentials
  5

Adding MooTools to Your Page(s)
Now that you have the JavaScript file, you need to add it to your HTML
documents. Once you’ve done that, you can write JavaScript using
MooTools methods and classes. Here’s a simple example document that
illustrates how to add MooTools to your page(s):
Coding for Reuse
If you divide your code into two types—implementation code and classes
that are designed for reuse—you’ll find that your work can pay off for
faster development, maintenance, and a smaller code base that has to be
delivered to your users.
If you are going to write code to animate several images in a carousel,
consider writing a generic class that does that, with variables and options
passed in and set whenever the class is invoked. When you explore the
6
MooTools Essentials

section of this book on classes (see Chapter 7), you’ll see how these can be
extended and reused later.
What’s more, using generic classes allows you to make your
implementation code a much more brief set of instructions that just creates
instances of these classes for individual pages. You can then deliver two
JavaScript files to every page on your site: the common code that includes
MooTools and the implementation code for that specific page. The fewer
files you send to the browser, the faster your site will be; and with your
code clearly separated, you’ll find it much easier to maintain and reuse.
Compression
As mentioned earlier, you can download MooTools with compression
enabled or unaltered. When developing, it’s helpful to use the
uncompressed code so that errors yield actual line numbers, and the code is
readable.
The same holds true for the code you write. If you have a lot of JavaScript
on your site, it’s courteous to your visitors to compress the code you write
in addition to MooTools.
Using the YUI Compressor
The way that MooTools itself works is a good illustration of how to
maintain and deliver JavaScript. It’s much easier to maintain a set of small
files that each contain a specific set of functionality, but delivering these
files individually will slow down your site.

MooTools Essentials
7

MooTools provides SVN (a.k.a. Subversion) access to download these
small files, but offers a download page that lets you download a
compressed version of the files you need for your application.
In my own experience, this practice also works well for your code.
In my environment, I use a set of shell scripts that will concatenate a
library from the various source files that I maintain, and then process the
resulting file through the YUI Compressor to output the compact file.
Here’s an example of what that kind of script looks like:
cat "MooTools/1-11/Core/Core.js" > global.js
cat "MooTools/1-11/Class/Class.js" >> global.js
cat "MooTools/1-11/Class/Class.Extras.js" >> global.js
cat "mycode/slideshow.js" >> global.js
cat "mycode/carousel.js" >> global.js
java -jar yuicompressor-2.2.4.jar –o
global.compressed.js global.js
The result is a set of two files: global.js, which is uncompressed, and
global.compressed.js, which is much smaller. I can use the former for
development and debugging and the latter for delivery to the visitors of my
site.
When editing the files that I maintain, I can just save my changes, run the
shell script, and refresh my browser.
There are more sophisticated methods for doing this sort of thing with Ant
targets and the like, but if you know how to author those, this simple
example should be enough to illustrate the concept.
8
MooTools Essentials

Chapter 2: Reviewing MooTools
This book is divided into chapters that correspond with the functionality
found in the MooTools library so that you can easily use it as a reference,
by paging through to find the information you’re seeking. In this way, it is
Each chapter will cover a basic set of functionality (like effects, for
example) and feature the following:
  A short overview of the syntax of the methods and classes
  Code examples illustrating how to use the classes, methods, and functions
  A review of the important functionality provided and any nuances that will
help you use the it properly
In this manner, each chapter will attempt to illustrate not only how to use
MooTools, but also why it works the way it does.
Note
In all cases, it’s always a good idea to look at the MooTools
source code to gain a deeper understanding of how it works. There is no
better illustration of how to use MooTools than MooTools itself. Using the
library as a template for your own code will not only help you understand it
better, but also help you write your code in a Moo way.
MooTools File Structure
MooTools is broken up into numerous files to make it easy to download
only the part that you need for your page to work (see “Making Use of
MooTools’ Modular Design” in the Introduction). Part of the process of
organizing the code into the various libraries to make this modular design
possible requires that some functionality be split up. For example,

MooTools Essentials
  9

Core/Core.js is required for all of MooTools, and it includes numerous
shortcut methods as well as the base functionality for the Hash native
object. But Hash has its own script in Native/Hash.js, which contains
much more functionality. The functionality in Core.js is there just to
support other scripts that need it.
This splitting up of functionality isn’t reflected in the organization of this
book; in order to illustrate how to use the library, it’s best that I keep ideas
that are similar next to each other.
In each section that I illustrate a method, function, or class, I’ll also note its
location in the library whenever it isn’t obvious so you can find it in the
code.
Manifest of MooTools Scripts
Here is a list of every file in the MooTools library, along with what it does
and when you’ll use it.
MooTools is broken into two separate libraries: The “Core” and plug-ins,
which MooTools has in a repository called “More.”
The MooTools Core
When you visit MooTools and download the main library (the Core), you’ll
get all the following files.
Core/Core.js
What it does: Defines the Native class and numerous helper functions
used throughout MooTools. Core.js also defines the base functionality for
the Hash and Array native objects.
When you’ll use it: MooTools uses all the methods in this script. You
yourself will use several of them, though likely not the Native function, as
MooTools instantiates instances of the Native class for nearly all the
10
MooTools Essentials

native objects (specifically, MooTools creates them for Array, Element,
Event, Function, Hash, Number, and Function).
Core/Browser.js
What it does: Defines the Browser hash and identifies various properties
about the client running library (i.e., the user’s browser). Browser.js also
defines the Window and Document native objects.
When you’ll use it: MooTools itself uses the methods of this script for
scripts that help fix browser quirks. You’ll need to reference the properties
and methods defined in this script whenever you have your own code that
has conditionals based on the client (e.g., if you have code that should work
differently for IE than it does in Safari or Firefox).
Class/Class.js
What it does: Defines Class and its methods and properties.
When you’ll use it: Class is a powerful method for creating reusable
functionality. This method is at the heart of MooTools, so you’ll use it all
the time whether you’re authoring a class or instantiating one.
Class/Class.Extras.js
What it does: Defines the Events, Chain, and Options classes.
When you’ll use it: The three classes defined in this script can be
implemented into others, providing common, reusable patterns employed
throughout MooTools and useful in your own work.
Element/Element.js
What it does: Extends the Element native object, providing numerous
shortcut, selection, and initialization methods.

MooTools Essentials
11

When you’ll use it: Like all the scripts in the Native directory,
Element.js extends the native DOM Element. This is one of the most
important scripts in the library. The Element files are located in their own
directory (instead of in the Native directory with the other scripts) because
Element.*.js requires all the other Native scripts.
Element/Element.Dimensions.js
What it does: Extends the Element native with methods to inspect the
location and dimensions of that element.
When you’ll use it: Whenever you need to work with size, scrolling, or
positioning of elements and the document.
Element/Event.js
What it does: Extends the native Event object with element-specific
methods, defines the functionality to create custom events, and includes the
mouseenter, mouseleave, and mousewheel custom events.
When you’ll use it: Whenever you attach an event listener to a DOM
element (click, load, mouseover, etc.), the method you attach is, by default,
passed the event that fired it. Element.Events.js extends elements to
make attaching events and managing the Event object easier.
Element/Style.js
What it does: Defines methods used to alter the style properties of
elements.
When you’ll use it: Whenever you wish to alter the style of a DOM
element, you’ll use the methods defined in Element.Style.js.
Fx/Fx.js
What it does: Defines the base functionality for all the Fx.*.js scripts.
12
MooTools Essentials

When you’ll use it: You probably won’t use Fx.js directly. It’s only
useful if you wish to write your own effect extension.
Fx/Fx.CSS.js
What it does: Defines the animation logic for transitioning style
properties.
When you’ll use it: It’s used indirectly through Fx.Tween, Fx.Morph, and
Fx.Elements, but, like Fx, it’s unlikely that you’ll use it directly unless
you extend it to write your own effect.
Fx/Fx.Morph.js
What it does: Defines the Fx.Morph effect.
When you’ll use it: Fx.Morph is used to transition more than one CSS
property at once (e.g., height and width).
Fx/Fx.Transitions.js
What it does: Defines numerous transitions that can be used by any effect.
When you’ll use it: Fx (and therefore the classes that extend it) comes with
a basic linear transition, but Fx.Transitions.js defines a dozen more
including bounce, circ, expo, elastic, and others. Additionally,
Fx.Transitions.js defines methods that you can use to write your own.
Fx/Fx.Tween.js
What it does: Defines the Fx.Tween effect.
When you’ll use it: Fx.Tween is used to transition a single CSS property
(height, width, color, etc.).
Native/Array.js
What it does: Extends the Array native with additional methods.

MooTools Essentials
13

When you’ll use it: Whenever you work with data in array format, you’ll
benefit from the 20 or so methods added to its prototype by Array.js.
Native/Event.js
What it does: Extends the native Event object to grant it cross-browser
stability.
When you’ll use it: Event.js works well with Element.Event.js. The
former focuses on extending the Event native with properties and methods
to remove the inconsistencies found in different browser implementations
of the Event object, while the latter implements methods and properties on
the Element native to make it easy to attach event listeners and manage
them.
Native/Function.js
What it does: Extends the native Function object with numerous methods
that enhance functional programming.
When you’ll use it: You’ll use the methods added by MooTools to the
native Function object constantly. Functional programming (see
“Functional Programming (a.k.a. Lambda)” in the Appendix) requires that
you interact with Function objects constantly, and Function.js includes
several methods that make that management easier.
Native/Hash.js
What it does: Extends the native Object when you initialize it (new
Hash()).
When you’ll use it: Because all native objects in JavaScript inherit from
Object, modifying its prototype is universally considered bad form.
MooTools therefore provides an enhanced Object with various properties
and methods applied to it, just like it does for the other natives (Array,
Function, etc.). However, unlike the other native scripts, this script
14
MooTools Essentials

requires you to initialize any object that you wish to apply these methods
to.
Native/Number.js
What it does: Extends the native Number object to add numerous helpful
methods.
When you’ll use it: Whenever you’re doing math or managing numbers or
even just iterating a function a specified number of times, the methods in
Number.js will help make the process simpler.
Native/String.js
What it does: Extends the native String object to add numerous helpful
methods.
When you’ll use it: Like Number.js, String.js makes inspecting and
altering strings much easier.
Request/Request.js
What it does: Defines the Request class, an XMLHttpRequest wrapper.
When you’ll use it: This is MooTools’ Ajax class. It provides a rich
interface to the native XMLHttpRequest, or XHR.
Request/Request.HTML.js
What it does: Extends the Request class to add functionality specific to
updating content in the DOM with HTML retrieved from the server.
When you’ll use it: Whenever your Ajax request retrieves HTML that is
used to update the contents of a DOM element (a common practice).

MooTools Essentials
15

Request/Request.JSON.js
What it does: Extends the Request class to automatically manage the
receiving of JSON data.
When you’ll use it: Whenever you are receiving data in a JSON notation
(the result of converting a native JavaScript Object to a String).
Selectors/Selectors.js
What it does: Adds advanced CSS querying capabilities for selecting
elements.
When you’ll use it: Element.js includes the $$ function to collect
objects out of the DOM as well as element methods such as
Element.getElements. These methods by default only accept tag names
for filters ($$('div') gets all the divs on a page). When you include
Selectors.js, you can use any CSS expression with these methods to
select elements from the DOM.
Utilities/Cookie.js
What it does: Defines a set of methods in the Cookie namespace for
managing cookie values.
When you’ll use it: Whenever you want to read, write, or remove cookies.
Utilities/DomReady.js
What it does: Defines the domready custom event.
When you’ll use it: The domready event is used to delay the execution of
your page initialization code until after all the HTML has been delivered to
the browser and is available in memory. It’s crucial that you don’t interact
with the DOM until after it’s loaded using this custom event. The onload
event on the window can be used the same way, but has the negative
quality of waiting for every image to load before running.
16
MooTools Essentials

Utilities/JSON.js
What it does: Contains methods for managing data in JSON format.
When you’ll use it: Whenever you need to encode or decode JSON.
Utilities/Swiff.js
What it does: Serves as a wrapper for embedding SWF movies. Supports
(and fixes) external interface communication.
When you’ll use it: Whenever you wish to embed SWF (Flash) objects.
The MooTools Plug-Ins: “More”
When you download the plug-ins for MooTools, you can choose any of the
following files to include. These are the “official” MooTools plug-ins,
though numerous third-party plug-ins are also available (which I cover in
Chapter 12).
Fx/Fx.Elements.js
What it does: Defines the Fx.Elements effect.
When you’ll use it: When you need to alter CSS properties on several
elements at once, it’s more efficient to use a single instance of
Fx.Elements than to have several instances of Fx.Tween or Fx.Morph.
Fx/Fx.Scroll.js
What it does: Defines the Fx.Scroll effect.
When you’ll use it: Fx.Scroll is used to smoothly scroll any DOM
element, including the window.

MooTools Essentials
17

Fx/Fx.Slide.js
What it does: Defines the Fx.Slide effect.
When you’ll use it: The Fx.Slide effect moves an element in and out of
view kind of like window blinds. A container element crops out the view of
the element as it slides in or out.
Drag/Drag.js
What it does: Defines the base functionality for dragging items in the
browser window.
When you’ll use it: Any time you want to have an element on your page
that the user interacts with by dragging, you’ll use Drag.js. You can
attach any functionality to the dragging action, from resizing, to moving,
to, say, changing the color of something.
Drag/Drag.Move.js
What it does: Provides support for the constraining of draggables to
containers and droppables.
When you’ll use it: If part of the drag functionality that you use requires
the ability to drop things into containers and you wish to constrain the
behavior to an area, Drag.Move.js provides basic methods to do this.
Utilities/Assets.js
What it does: Provides methods to dynamically load JavaScript, CSS, and
image files into the document.
When you’ll use it: If you’re injecting a lot of assets into the DOM,
Assets.js provides some easy methods to make the process a little easier.
18
MooTools Essentials

Utilities /Color.js
What it does: Defines the Color class for creating and manipulating colors
in JavaScript. It supports conversions from HSB to RGB and vice versa.
When you’ll use it: If you’re doing color calculations, the Color class
contains numerous methods that are helpful.
Utilities/Group.js
What it does: Defines the Group class used to monitor a collection of
events.
When you’ll use it: Whenever you have numerous classes or elements that
you wish to monitor as a collection. For instance, you would use this class
if you want to execute a function only after each div on the page has been
clicked.
Utilities/Hash.Cookie.js
What it does: Defines the Hash.Cookie class.
When you’ll use it: If you have a map of keys/values that you need to
store in a cookie, Hash.Cookie automates the process by creating or
retrieving the cookie and then providing methods to get and set the values,
automatically updating the cookie in the process.
Interface/Accordion.js
What it does: Defines the Accordion UI class.
When you’ll use it: If you have a long definition list (like an FAQ) or a
menu that needs to expand, the Accordion class provides a nice way to
make that interactive.

MooTools Essentials
19

Interface/Scroller.js
What it does: Defines the Scroller class, which scrolls the contents of
any element (including the window) when the mouse reaches the element’s
boundaries.
When you’ll use it: If you have draggable elements on the page, and they
should be draggable to a location that is scrolled either off screen (in the
case of the window) or out of view (in the case of an overflowed DOM
element), you need some method for users to drag things from their
location to their off-screen targets. The Scroller class provides the
functionality to automatically scroll the DOM element or the window when
users drag an element near the boundaries of the area that needs to scroll.
Interface/Slider.js
What it does: Defines the Slider class with two elements: a knob and a
container.
When you’ll use it: This basic UI component is useful when you want
users to select a value from a set of values—like how big the thumbnails on
a page should be or the maximum price they are willing to pay for
something.
Interface/SmoothScroll.js
What it does: Defines the SmoothScroll class.
When you’ll use it: SmoothScroll automatically converts any name
anchors on the page (links that reference a different location on the same
page with the # value) to animate the window so it scrolls smoothly to the
target location instead of just jumping there.
20
MooTools Essentials

Interface/Sortables.js
What it does: Defines the Sortables class.
When you’ll use it: Sortables lets you easily convert a collection of
elements into a draggable, sortable list. You can have more than one list so
that users can drag items from one list to another, dropping the item into a
new location in the new list.
Interface/Tips.js
What it does: Defines the Tips class.
When you’ll use it: The Tips class makes it easy to display tooltips when
users hover their mouse over a given DOM element.

MooTools Essentials
21

Chapter 3: Shortcuts and Helpful
Functions
MooTools has numerous stand-alone functions that make tasks easier and
take fewer keystrokes. Most of these functions are used by MooTools itself
and are located in Core/Core.js, which is required by all of MooTools.
Others are more specific to specific kinds of tasks, and you’ll only have
them available if you include the scripts that are needed to accomplish
those tasks.
Determining the Type of an Object: $type
JavaScript is a loosely typed language, which allows for a great deal of
expressiveness, but also results in a lot of headaches. On top of this,
JavaScript does a lot of type coercion (see “Type Coercion—‘Falsy’ and
‘Truthy’ Values” in the Appendix).
Thankfully, MooTools fixes this for us developers with the $type function.
$type :: Core/Core.js
What it does: $type returns the type of the object that is passed in.
Usage:
$type(object) //"string", "object", or "array", etc.

MooTools Essentials
23

Example:
var ninja = {
wealth: 0,
getPaid: function(howMuch){
if ($type(howMuch) == "string") {
ninja.wealth += parseInt(howMuch);
} else if ($type(howMuch) == "number") {
ninja.wealth += howMuch;
}
}
};
When you’ll use it: Often, you’ll be unsure whether your method is being
passed a string or a number, a DOM element or its ID, and so on. $type
returns the type of an object as a string ('function', 'string', etc.) or
false if the object is not defined. Here are the values it returns (all strings
unless noted):
  “element” if the object is a DOM element node
  “textnode” if the object is a DOM text node
  “whitespace” if the object is a DOM whitespace node
  “arguments” if the object is an arguments object
  “object” if the object is an object
  “array” if the object is an array
  “string” if the object is a string
  “number” if the object is a number
  “boolean” if the object is a Boolean
  “function” if the object is a function
  “regexp” if the object is a regular expression
  “class” if the object is a MooTools class
24
MooTools Essentials

  “collection” if the object is a native HTML elements collection, such as
childNodes, getElementsByTagName, and so on
  “window” if the object is the window object
  “document” if the object is the document object
  “date” if the object is a date
  false (Boolean) if the object is not defined or is none of the above
Checking Whether Values Are Defined: $defined,
$chk, and $pick
Often in your code, you’ll need to determine whether a variable has been
defined by the user. MooTools gives you some helpful methods to simplify
this basic task.
$defined :: Core/Core.js
What it does: $defined checks to see whether a variable is defined (i.e.,
not null or undefined).
Usage:
  $defined(object)
Example:
function myFunction(arg){
if($defined(arg)) alert('The object is defined.');
else alert('The object is null or undefined.');
}
When you’ll use it: This is just a shortcut for
value == undefined
Because JavaScript performs type coercion (see “Type Coercion—‘Falsy’
and ‘Truthy’ Values” in the Appendix), you can’t just evaluate a value to
see if it has a value. All the following examples perform type coercion:

MooTools Essentials
  25

if ("") ... //false
if (0) ... //false
if (null) ... //false
function test(value){
return !!value;
};
test(); //No value passed, so it is undefined,
//and test() returns false
As these examples demonstrate, $defined is a shortcut to determine
whether a value has been set at all.
$chk :: Core/Core.js
What it does: $chk checks to see whether a value is defined or is zero.
Usage:
  $chk(value)
Example:
var ninja = {
wealth: 0,
getPaid: function(howMuch){
if ($chk(howMuch)) wealth += howMuch;
}
};
When you’ll use it: Much like $defined, $chk helps you manage type
coercion. $chk will still return false for null, undefined, false, and
empty strings, but it won’t return false for zero.
$pick :: Core/Core.js
What it does: $pick returns the first defined argument passed in or null.
You can pass as many arguments to $pick as you like, and the first one
that is not null or undefined will be returned.
26
MooTools Essentials

Usage:
$pick(var1, var2, var3, etc.)
Example:
var ninja = {
chooseSide: function(isGood){
ninja.isGood = $pick(isGood, ninja.side, false);
}
};
In this example, when the method chooseSide is executed, the side of the
ninja is set to be the value passed in. If no value is passed in, the side is
set to the current state. If there is no current state, the side defaults to
ninja.isGood = false.
When you’ll use it: $pick is yet another shortcut. You can express its
basic concept as a simple conditional:
function test(var1, var2){
if(var1 == undefined) return var2;
else return var1;
};
Because $pick lets you pass in numerous arguments, it allows for
numerous of these conditionals. In the preceding ninja example, I use
$pick for three values. If I were to express this as a set of if/else
conditionals, it would look like this:
var ninja = {
chooseSide: function(isGood){
if ($defined(isGood)) {
ninja.isGood = isGood;
} else if (!$defined(ninja.side)) {
ninja.isGood = false;
}
}
};

MooTools Essentials
27

The more things you need to consider, the more conditionals you have to
add. $pick is shorthand for all that logic.
Tip
You can also use the logical “or” (||) for most of these
operations. For example
var ninja = {
setName: function(name){
ninja.name = name || ninja.name ||‘fred’;
}
};
Here we store name as the value passed in, or the current value of
ninja.name, or a default (fred). You should use $pick whenever a valid
value is “falsy” (zero, an empty string, the Boolean false, etc.).
Working with Objects: $extend, $merge, and
$unlink
The native object—a Hash-like set of key/value pairs—is something that
we developers use often in modern JavaScript. Unfortunately, the language
doesn’t have many tools to help you manage the data in them.
JavaScript objects do not contain any native methods or properties, and
while MooTools does give us a more powerful version of this (with Hash—
see “Objects (a.k.a Hash)” in Chapter 4), it doesn’t alter the prototype of
object (which is an important rule in JavaScript, as all other objects—
including functions and strings and arrays—inherit from the object
prototype).
To make things easier to work with native objects, MooTools provides the
following core methods.
28
MooTools Essentials

$extend :: Core/Core.js
What it does: $extend copies all the properties from the second object
passed in to the first object.
Usage:
$extend(object1, object2)
Example:
var firstObj = {
'name': 'John',
'lastName': 'Doe'
};
var secondObj = {
'age': '20',
'sex': 'male',
'lastName': 'Dorian'
};
$extend(firstObj, secondObj);
//firstObj is now:
//{'name': 'John', 'lastName': 'Dorian', 'age': '20',
// 'sex': 'male'};
When you’ll use it: The functionality defined in $extend is pretty
straightforward—if you need to blend the properties of one object into
another, $extend will do that for you. You should use $extend any time
that you need to manage objects this way except when the objects being
blended contain as properties other objects or arrays.
The problem is that if you use $extend on objects that do contain arrays or
other objects as properties, you will link them together.

MooTools Essentials
29

Here’s a simple illustration in code:
var defaultNinja = {
  weapons: ['sword', 'star', 'stealth'],
  equipment: {
  grapple: 'iron',
  rope: '40 meters'
}
};
var goodNinja = {
  specialAbility: 'warrior spirit',
  weakness: 'kittens'
}
$extend(goodNinja, defaultNinja);
//Now goodNinja contains the weapons array and the
//equipment object
In this example, both goodNinja and defaultNinja contain properties for
weapons and equipment because $extend copies them from the former
into the latter.
However, because they are of type array and object, respectively, they
are linked—they are the same objects. If you subsequently added flying
guillotine to goodNinja.weapons, both goodNinja.weapons and
defaultNinja.weapons would contain that value.
This is due to the way JavaScript assigns variables to memory. Consider
this code:
var x = 'foo';
var y = x;
x = 'bar';
//x != y;
Everything is fine if you’re just assigning values to variables. But when
you’re dealing with objects, the equals sign means something a little
different. If I say that two objects are equal to each other and then change a
30
MooTools Essentials

property of one of them, I change that property for both. Consider the
following:
var myArmy = {
  ninjas: {
  side: 'evil'
}
};
var yourArmy = {};
yourArmy.ninjas = myArmy.ninjas;
//ninjas here are the same object

yourArmy.ninjas.side = 'good';
//myArmy.ninjas.side == 'good';
//yourArmy.ninjas.side == 'good';
In this example, you can see that the property ninjas for both myArmy and
yourArmy is assigned to the same object. These properties are the same
object. Changing the value of that object using either reference changes it
for both.
This is why $extend is only useful for objects that do not contain
properties that are also objects or arrays (arrays have the same problem),
and why you should use $merge when you have members that are
themselves objects or arrays.
It’s important to note that this isn’t a fault with $extend or JavaScript; it’s
how JavaScript is supposed to work. Most of the time it’s an asset, but
occasionally when you encounter these kinds of links unintentionally, you
can get some unintended results.
$merge :: Core/Core.js
What it does: $merge combines any number of objects recursively,
dereferencing them or their subobjects from their parents.

MooTools Essentials
  31

Usage:
$merge(object1, object2, object3, etc.)
Example:
var obj1 = {a: 0, b: 1};
var obj2 = {c: 2, d: 3};
var obj3 = {a: 4, d: 5};
var merged = $merge(obj1, obj2, obj3);
//Returns {a: 4, b: 1, c: 2, d: 5}
//(obj1, obj2, and obj3 are unaltered)

var nestedObj1 = {a: {b: 1, c: 1}};
var nestedObj2 = {a: {b: 2}};
var nested = $merge(nestedObj1, nestedObj2);
//Returns {a: {b: 2, c: 1}}
When you’ll use it: Any time you need to combine two objects that
contain members that are objects or arrays, you should use $merge to
ensure you don’t link the result to the originals. $merge is slower than
$extend, so you shouldn’t overuse it, but care should be taken that you use
$merge when you need to (see the section “$extend :: Core/Core.js” section
earlier in this chapter on this topic).
As outlined in the discussion on $extend, $merge lets you blend objects
together, but is recursive when it finds properties that are also arrays or
objects. Unlike when you use $extend, you don’t have to worry about
linking the objects together, but you pay a performance price for this
recursion.
Also, unlike $extend, $merge lets you pass it any number of objects. If
any two objects contain the same properties (but different values), the last
one wins.
32
MooTools Essentials

For example:
ninja.garb = $merge({
  mask: 'red',
  sash: 'black'
}, {
  sash: 'white'
}); //Returns {mask: 'red', sash: 'white'}
When $merge encounters properties that are objects, it will execute itself
on that property, blending the two properties together as illustrated in the
second example in the preceding “Example” section.
Finally, unlike objects passed to $extend, objects passed to $merge are not
altered. Instead, the resulting merged object is returned by the method. If
you want to assign the result to one of the objects passed in, you can do
that easily enough:
object1 = $merge(object1, object2);
$unlink :: Core/Core.js
What it does: $unlink will return a copy of an object or array that
contains no links to the original.
Usage:
$unlink(array)
$unlink(object)
Example:
evilNinja.desires = ['money', 'a worthy opponent',
'friends'];
goodNinja.desires = $unlink(evilNinja.desires);
goodNinja.desires.splice(0,1);
//goodNinja doesn't need money
If $unlink weren’t included in this example, the desires of evilNinja
would point to the same array as the desires of goodNinja, and altering

MooTools Essentials
  33

one would alter the other. Including $unlink creates a copy of the array
(or object) and breaks any of these links.
When you’ll use it: MooTools bakes this method into much of its
functionality, so it’s not something you’re likely to call upon very often.
Whenever you need a copy of an array or object that contains as members
other arrays or objects, you’ll need to unlink them to ensure you don’t
pollute the original.
Iterable Helpers and Shortcuts: $arguments, $each,
$splat, $A, and $H
Both arrays and objects contain members that you’ll often find the need to
iterate over. You can use the standard for loop, but this isn’t a very
functional way of doing things. There are some advantages to iterating over
a collection and executing methods on those members (see “Functional
Programming (a.k.a. Lambda)” in the Appendix).
The current specification for JavaScript includes more modern iteration
methods like Array.each and others, but only certain browsers offer
native support. MooTools extends arrays and objects (via its Hash class)
with these methods, but it also supplies a few stand-alone iteration methods
in its core that can be used on their own.
$arguments :: Core/Core.js
What it does: The $arguments function creates a function that returns the
passed argument according to the index passed in.
Usage:
var argument = $argument(i);
Example:
var secondArgument = $arguments(1);
console.log(secondArgument('a','b','c')); // Alerts b
34
MooTools Essentials

When you’ll use it: You will likely not find yourself using it, so if you
don’t get why you’d want it, don’t sweat it. This function is used within
MooTools, which has a lot of functionality that’s highly abstract.
$arguments is an example of one of these abstract concepts that gets used
in the framework itself, but it’s highly unlikely that you’ll find a reason in
your own work to use it.
$each :: Core/Core.js
What it does: $each is used to iterate through iterables that are not regular
arrays, such as built-in getElementsByTagName or Element.childNodes
calls, arguments of a function, or objects.
Usage:
$each(arguments, function(value, [index or key]){
  alert(value);
}, bin
Example:
//Simple example with function referencing each value
$each([1,2,3], function(value){
alert(value); //Alerts 1, 2, 3
});
//Same concept but the function also references
//the index of each value
$each([1,2,3], function(value, index){
  alert('the value at index ' + index + ' is ' + value);
//Alerts
//"the value at index 0 is 1"
//"the value at index 1 is 2"
//"the value at index 2 is 3"
});
//This example illustrates binding

MooTools Essentials
  35

Usage:
  $splat(object)
Example:
$splat('hello') //['hello']
$splat([1,2,3]) //[1,2,3]
var ninja = {
fight: function(who){
//We don't know if who is a single enemy
//or an array of them
  $splat(who).each(function(enemy){
  enemy.isAlive = false;
});
}
};
When you’ll use it: $splat is usually written for interfaces where it’s
convenient to be able to hand a method a single thing or a bunch of them. If
you are calling such a method and you have one thing, it’s nice to just be
able to call the method with that one thing. But the method itself has to deal
with getting an array or a single variable. $splat will take the object
passed to it and, if it’s an array, just return the object; otherwise, it’ll add
the object to an empty array and return that.
$A :: Core/Core.js
What it does: $A creates an array from an iterable object (such as the
arguments of a method or a DOM node collection). If the item passed in is
an array, $A will simply return it.
Usage:
var myArray = $A(iterable);

MooTools Essentials
  37

Example:
var ninja = {
weapons: [],
equip: function(){
$A(arguments).each(function(weapon){
ninja.weapons.push(weapon);
});
}
};
ninja.equip("sword", "star", "smoke");
When you’ll use it: $A is mostly used by MooTools for applying the
Array methods to iterable objects, but it can also be useful if you want to
have a function or method that takes an unspecified number of arguments
by referencing $A(arguments), as in the preceding example. You could
make the function require an array as its argument, but it might be easier to
use if you don’t. For example, see the discussion on $pick in the section
“Checking Whether Values Are Defined: $defined, $chk, and $pick” earlier
in this chapter.
$H :: Core/Core.js
What it does: $H is a shortcut to initialize an instance of Hash.
Usage:
$H(object)
Example:
var fooHash = $H({foo: 'bar'});
When you’ll use it: This is just a shortcut for new Hash(obj), which
returns an instance of Hash (see “Objects (a.k.a. Hash)” in Chapter 4 for
more on Hash).
38
MooTools Essentials

Other Shortcuts: $clear, $empty, $lambda,
$random, $time, $try
In addition to the iteration and inspection shortcuts listed previously in this
chapter, MooTools provides a few other core tricks to make using
JavaScript a little more pleasant. With the exception of these stand-alone
functions (and a few others in the library), almost all the other functions
provided by MooTools are in methods on native objects (like Array or
String) or MooTools classes (like effects).
$clear :: Core/Core.js
What it does: $clear clears a timeout or an interval.
Usage:
$clear(timer)
Example:
var timer = setTimeout(ninjas.attack, 500);
$clear(timer); //Belay that order!
When you’ll use it: This is just a shortcut for clearTimeout and
clearInterval.
$empty :: Core/Core.js
What it does: $empty is, surprise, an empty function. Typically, it is used
as a placeholder inside event methods of classes.
Usage:
  var callback = $empty;

MooTools Essentials
  39

Example:
var ninja = {
afterAttack: $empty,
attack: function(enemy) {
enemy.isAlive = false;
ninja.afterAttack();
}
};
//Later
ninja.afterAttack = function(){
ninja.weep();
};
When you’ll use it: A common practice in MooTools is to define a
callback as an empty function (literally just function(){}). Then later,
the user writes some code that defines that callback as something else. In
the code that calls that callback, it doesn’t have to check to see whether the
user set the function or not. If the user didn’t set it, it’s still just an empty
function, and there’s no harm in executing it. $empty is just a shortcut for
function(){}.
$lambda :: Core/Core.js
What it does: $lambda creates an empty function that does nothing but
return the value passed, unless the passed-in item is a function, in which
case it calls that function.
Usage:
var returnTrue = $lambda(true);
40
MooTools Essentials

Example:
myLink.addEvent('click', $lambda(false));
//Prevents a link Element from being clickable.
var test = function(item){
return $lambda(item)();
//If item is not a function,
//lambda creates a function
//then we return the result of that function
};
When you’ll use it: Basically, $lambda saves you the time of figuring out
if a value is a function that returns a value or if it’s just a value. It’s a subtle
concept, and you may not find yourself using it.
$random :: Core/Core.js
What it does: $random returns a random number in a given range.
Usage:
$random(min, max)
Example:
var mortalKombat = {
contestants: [Scorpion, Sub-Zero, Ermac, Smoke,
Reptile, Noob Saibot, Rain],
play: function(player){
//The player fights a random opponent
player.fight(
$random(0, mortalKombat.contestants.length-1)
);
}
};
When you’ll use it: This is pretty straightforward. $random just gives you
a random number.

MooTools Essentials
41

$time :: Core/Core.js
What it does: $time returns the current time as a timestamp (an integer).
Usage:
$time()
Example:
var ninja = {
lastFight: 0,
fight: function(enemy){
//Is the ninja too tired?
if ($time() - ninja.lastFight < 1000) return;
//No! Fight!!!
enemy.isAlive = false;
ninja.lastFight = $time();
}
};
When you’ll use it: $time can be used for a lot of things. Basically, it’s
just a shortcut to new Date().getTime(), and it returns a large integer.
You can use it to measure the duration between events or to generate a
number that is unique for an event (provided you don’t have events firing
at a rate faster than one per millisecond).
$try :: Core/Core.js
What it does: $try will attempt to execute any number of functions,
returning either the return value of the first one that does not throw an error
or null if none of them succeed.
Usage:
$try (fn, fn, fn, etc.);
42
MooTools Essentials

Example:
var result = $try(function(){
return some.made.up.object;
//Fails - this is nonsense
}, function(){
return jibberish.that.doesnt.exist;
//More junk, throws errors
}, function(){
return 2+2;
}); //result == 4
When you’ll use it: $try is just another shortcut to save a little time. It’s a
functional programming way of looking at try/catch that basically does
the same thing, except you can run numerous functions through it.
Browser: Information About the Client
MooTools contains a set of useful shortcuts to information about the
visitor’s browser. All the engine detection is feature based (rather than
sniffing the client string, which is unreliable). There’s not a lot to explain
here, so I’ll just quote the documentation. You can reference this
information by referring directly to the attribute.
Example:
if(Browser.Engine.trident4) {
alert('Hey, IE6 was released in 2001! UPGRADE!');
}
Features:
  Browser.Features.xpath: (Boolean) true if the browser supports DOM
queries using XPath
  Browser.Features.xhr: (Boolean) true if the browser supports the native
XMLHTTP object

MooTools Essentials
  43

Engine:
  Browser.Engine.trident: (Boolean) True if the current browser is
Internet Explorer (any version)
  Browser.Engine.trident4: (Boolean) True if the current browser is
Internet Explorer 6
  Browser.Engine.trident5: (Boolean) True if the current browser is
Internet Explorer 7
  Browser.Engine.gecko: (Boolean) True if the current browser is
Mozilla/Gecko
  Browser.Engine.webkit: (Boolean) True if the current browser is
Safari/Konqueror
  Browser.Engine.webkit419: (Boolean) True if the current browser is
Safari 2/WebKit prior to and including version 419
  Browser.Engine.webkit420: (Boolean) True if the current browser is
Safari 3 (WebKit SVN Build)/WebKit after version 419
  Browser.Engine.presto: (Boolean) True if the current browser is Opera
  Browser.Engine.name: (String) The name of the engine
Platform:
  Browser.Platform.mac: (Boolean) True if the platform is Mac
  Browser.Platform.windows: (Boolean) True if the platform is Windows
  Browser.Platform.linux: (Boolean) True if the platform is Linux
  Browser.Platform.other: (Boolean) True if the platform is neither Mac,
Windows, nor Linux
  Browser.Platform.name: (String) The name of the platform
44
MooTools Essentials

Chapter 4: Native Objects
JavaScript contains numerous native object types (String, Array,
Function, Boolean, Element, etc.) that in many ways leave a lot to be
desired. What’s more, different browsers implement these objects
differently, making it difficult to write code that works across them all
without a lot of conditionals sniffing for different browsers.
MooTools implements functionality into the native objects to make them
both easier to work with (by adding shortcut methods) and more reliable
(by doing all the browser sniffing for you and providing you with a single
API that works for all browsers). These methods should always be used
rather than their native counterparts. MooTools will not only help you deal
with browser inconsistencies, but also protect you against things like
memory leaks. For more on this, see “Why You Should Use a JavaScript
Framework” in the Introduction.
Native.implement
In addition to altering these native objects, MooTools also allows you to
change them yourself. If there’s a method you wish String or Array had,
you can easily add it. The syntax is very similar to how implement works
with classes. Here’s an example:
String.implement({
alert: function(){alert(this);},
log: function(){console.log(this);}
});
"foo".alert() //Alerts "foo"
"foo".log() //Logs "foo"

MooTools Essentials
45

The implement method for both Class and Native work the same—they
alter the prototype of all the objects of that type. So the preceding example
doesn’t add the methods log and alert to a specific string, it adds it to all
of them by modifying the parent—the prototype of all strings.
This chapter will dig into the native objects:
  Array*
  Object (a.k.a. Hash)
  Function*
  Number*
  String*
  Event
  Element
For the items marked with an asterisk (*), you should use the literal
declarations for each. For example:
var numbers = [1,2,3]; //Yes
var numbers = new Array(1,2,3); //No
The exceptions are Event, Element, and Hash. For Hash, in particular, you
should use literal declarations for objects, but you’ll need to initialize those
objects into a Hash if you want to use the Hash methods:
//This is a standard object
var fruits = {
apple: 'red',
lemon: 'yellow',
grape: 'purple'
};
//Here is the same object as a hash:
var fruits = new Hash({
apple: 'red',
lemon: 'yellow',
46
MooTools Essentials

grape: 'purple'
});
fruits.each(function(color, fruit){
alert(fruit + 's are ' + color);
//Alerts apples are red, lemons are yellow, etc.
});
So even objects are declared as literals and only initialized as Hash
instances if you want the methods of Hash applied to them (see more in
“Objects (a.k.a. Hash)” later in this chapter).
Arrays
The native Array prototype gets a lot of love in MooTools. Arrays don’t
require any instantiation to acquire these methods (unless you’re working
with an iterable object that isn’t a true Array, like the arguments object—
see “Iterable Helpers and Shortcuts: $arguments, $each, $splat, $A, and
$H” in Chapter 3). This means you can (and should) use the literal
initialization for arrays. For example:
var numbers = [1,2,3];
numbers.each(function(value){
alert(value);
//Alerts 1, 2, 3
});
Array Methods
Arrays have numerous native methods (push, slice, pop, etc.), but not all
of these are easy to use, and many of them leave something to be desired.
In some cases, methods appear to have just been left out, like indexOf,
which is not in the original JavaScript 1.0 specification. It is, however, in
the 1.5 specification, which many modern browsers implement (Firefox,
Safari, Opera, etc.). MooTools adds numerous methods to Array. Most of
these are the methods defined in the 1.5 specification, and, for browsers
that already support these methods natively, MooTools doesn’t alter them.

MooTools Essentials
47

For older browsers that don’t support them, MooTools adds them so that
you can use them safely without having to worry whether they are present.
Here’s a quick rundown of all the Array methods:
METHOD TYPE
METHOD NAME
Iteration
each, filter, some, every, map
Introspection
indexOf, getLast, getRandom
Manipulation
erase, extend, include, combine,
associate, clean, flatten
Less commonly used
rgbToHex, link
Array :: Iteration Methods
The most used methods on Array will no doubt be employed to iterate over
thier properties. All of the iteration methods have the following in
common:
They take two arguments: a function to execute for each item in the array and
an optional object to which that function should be bound.
The function passed as the first argument is passed two arguments: the item
for that iteration and the index of it.
Let’s look at each, which you’ll use the most.
Array.each
What it does: Iterates over each item in an array and executes a method for
each item. The method is passed as arguments the value and the index of
that value in the array. Array.each takes an optional second argument for
an object to which to bind the passed-in method.
Usage:
myArray.each(function, bind);
48
MooTools Essentials

Example:
[1,2,3].each(function(value, index){
alert('the item at position ' + index +
' is ' + value);
//Alerts "the item at position 0 is 1",
//"...1 is 2", etc.
});
When you’ll use it: Using each instead of a for loop allows for a more
functional approach to your code (see “Functional Programming” in the
Appendix), but it also can make your code less verbose and easier to
manage.
The ability to bind something to that function is of course useful (see
“‘this’ and Binding” in the Appendix), and note that you don’t have to use
.bind on the function. For example:
//Incorrect
[1,2,3].each(function(value, index){}.bind(someObject));
//Correct
[1,2,3].each(function(value, index){}, someObject);
Also note that you don’t have to declare the index argument for the
function passed in if you aren’t making use of it. There’s no expense in
declaring it though, it just saves a few characters if you don’t need it.
//Here, index is unused
[1,2,3].each(function(value, index){alert(value);});

//I don't need index in my method, so there's
//no point in declaring it
[1,2,3].each(function(value){alert(value);});
The same is true for the bind object. If the contents of the method that you
pass to each do not make a reference to this, there’s no point in binding
the function to an object. Although there’s no real expense for doing it
anyway, there’s no benefit.

MooTools Essentials
49

Anonymous Methods vs. Named Functions
The preceding examples use an anonymous function, but there’s no reason
why you can’t pass the method a function that’s already defined. Consider
the following:
var say = function(msg) {alert(msg);};
[1,2,3].each(say); //Alerts 1, 2, 3
[1,2,3].each(function(msg){alert(msg);}); //Same thing
Other Iteration Methods
So each lets you iterate over the objects in an array, but what of the other
methods? So long as you understand how each works, you can apply the
same methodology to the other iteration methods. Here’s what they do:
Array.filter: This method returns a new array excluding items for which
the method passed to filter return something “falsy” (zero, empty string,
null, undefined, or false).
var evens = [1,2,3,4,5].filter(function(value, index){
return !(value % 2);
}); //Returns [2,4]
Array.some: This method returns a Boolean—true if the method passed to
some returns true at least once.
var atLeastOneOfTheseIsBiggerThanTwo = [1,2,3].some(
function(value, index){
return value > 2;
}
); //Returns true because 3 > 2
var oneIsEven = [1,3,5].some(function(value) {
return value % 2 == 0;
}); //Returns false, because 1,3,5 are each not even
Array.every: This method returns a Boolean—true if the method passed
to every returns true for each item in the array.

50
MooTools Essentials

erase, empty, and include, the array is also altered. So, for example,
myArray.erase(foo) alters myArray.
Array.erase: This method erases an item from the array.
['ninja', 'samurai', 'ninja'].erase('ninja')
//Returns ['samurai']
var warriors = ['ninja', 'samurai', 'ninja'];
warriors.erase('ninja'); //warriors = ['samurai']

//When an item is not found the array is unaltered
['shuriken', 'nunchucks', 'darts'].erase('katana')
//Returns ['shuriken', 'nunchucks', 'darts']
Array.empty: This method removes all the items from the array.
var foo = [1,2,3];
foo.empty(); //foo.length == 0
Array.extend: This method adds all the items in one array to the other
(allows duplicates).
var foo = [1,2,3];
foo.extend([2,3,4]; //foo = [1,2,3,2,3,4]
Array.include: This method pushes the value into the array if it’s not
already present.
['ninja', 'samurai'].include('kung-foo master')
//Returns ['ninja', 'samurai', 'kung-foo master']
['ninja', 'samurai'].include('ninja')
//Returns ['ninja', 'samurai']
var warriors = ['ninja', 'samurai'];
warriors.include('kung-foo master');
//warriors = ['ninja', 'samurai', 'kung-foo master']
52
MooTools Essentials

All of the following methods return a new array to you:
Array.combine: This method combines two arrays without duplicates.
Note that combine will exclude any duplicates found in the array passed in.
['ninja', 'samurai'].combine(['ninja',
'kung-foo master'])
//Returns ['ninja', 'samurai', 'kung-foo master']
Array.associate: This method returns an object of keys/values where the
passed-in array becomes the keys.
['good', 'evil'].associate(['samurai', 'ninja']);
//Returns {samurai: 'good', ninja: 'evil'}
Array.clean: This method is a shortcut to a version of Array.filter
that simply returns the value as its condition.
[null, 0, "", false, true].filter(function(value){
return value;
});
//Returns [true], as all the other values are "falsy"
[null, 0, "" , false, true].clean(); //Same result
Array.flatten: This method flattens an array of arrays into a single array,
returning a new array.
var myArray = [1,2,3,[4,5, [6,7]], [[[8]]]];
var newArray = myArray.flatten();
//newArray is [1,2,3,4,5,6,7,8]
Objects (a.k.a. Hash)
JavaScript has a basic object type—a hash or map—for storing values in
a single memory space. The language extends this very basic object for
nearly all the other types in the library, so, for example, a function is also
an object.
Unlike other natives in the language, MooTools does not extend the
object prototype to add helper methods, and neither should you. This is

MooTools Essentials
53

due to the way you iterate over the items in an object. Here’s what it looks
like in plain vanilla JavaScript:
var ninja = {
weapon: 'sword',
equipment: 'rope'
};
for (var prop in ninja){
alert("The ninja's " + prop + " is a " + ninja[prop]);
}
This example will send an alert that the ninja has a sword and a rope.
However, if you extend the object prototype, you would get those
properties too. Because this affects every type of object, it’s considered
forbidden—a no-no.
But working with objects is something developers do often in JavaScript,
and it’s a hassle to not have the same kind of helper methods that
MooTools offers for the other native types. To remedy this situation,
MooTools offers the Hash class. By instantiating this class with an object,
you get a new item that contains the properties of your object and the
helper methods.
This means that if you want to add methods to an object, you must
initialize it as a special extended type of object, and that’s what Hash does.
When you invoke new Hash(object), you are returned a copy of the
object, but now it has new properties—methods that you can use to manage
and inspect the data in the object.
Hash
What it does: Extends the native object (as in {foo: bar}) in JavaScript
to add iteration methods.
Core.js declares the Hash class specifically for the iteration method each
because it’s used in other scripts in the library, and so it has to be defined
54
MooTools Essentials

in Core.js. But because Hash is used liberally in MooTools, you’ll likely
include Native/Hash.js in any code you write.
Usage:
new Hash({foo: 'bar'});
$H({foo: 'bar'}); //$H is just a shortcut for new Hash
Example:
var ninjas = new Hash({
red: {side: 'unknown'},
black: {side: 'evil'},
white: {side: 'good'}
});
ninjas.each(function(value, key){
alert(key + ' ninja is on the side of ' + value.side);
});
When you’ll use it: Hash extends a native JavaScript object to add
methods to it that can be used to manage its data and to iterate over it.
$H
What it does: Serves as a shortcut for new Hash().
Usage:
var myHash = $H({foo: 'bar'});
//Same as
var myHash = new Hash({foo: 'bar'});
Hash Methods
MooTools adds numerous methods to objects when you include
Native/Hash.js, but Core/Core.js only adds the few that are required
for everything in the library to work. Given how widely used it is, you’ll
likely have Hash.js in your library.

MooTools Essentials
55

Much like the Array methods, the Hash methods, listed here, are mostly
used for iteration and introspection:
METHOD TYPE
METHOD NAME
Iteration
each, filter, some, every, map
Introspection
has, keyOf, hasValue,
toQueryString, get, getClean,
getKeys, getLength, getValues
Manipulation
set, extend, combine, erase, empty,
include
Hash :: Iteration Methods
Hash has all of the same iteration methods that Array uses, and they work
exactly the same way with one distinction: the function passed to the
method does not receive the value and the index but instead the value and
the key. Let’s look at Hash.each:
Hash.each
What it does: Lets you iterate over each member of a hash and perform a
function for each item, much like Array.each. The bind argument is
optional (as with Array.each). The passed-in function will be executed for
each item in the hash, and it will be passed as arguments the value and the
key of that value in the hash.
Usage:
myHash.each(function(value, key){/*your code*/}, bind);
//bind is optional
56
MooTools Essentials

Example:
//A conversation between two people arriving for work
$H({
goodNinja: 'Ralph',
evilNinja: 'Sam'
}).each(function(value, key) {
alert(key + ': Morning ' + value + '.');
//Alerts
//"goodNinja: Morning Ralph. "
//"evilNinja: Morning Sam. "
});
When you’ll use it: Whenever you have an object of key/value pairs and
need to iterate over them, it’s easier to use Hash.each than it is to use a
for loop. In addition to the easier syntax, you have the ability to define
scope (with binding) and use closures (see “Closures,” “Functional
Programming (a.k.a. Lambda),” and “‘this’ and Binding” in the Appendix).
Tip
You can iterate quickly over an object without using Hash with
$each:
$each(data, function(value, key) {...}[, bind]);
Using $H.each requires about the same effort:
$H(data).each(function(value, key{...}[,bind]);
All the other iteration methods for Hash follow this same pattern and do the
same things they do for Array.

MooTools Essentials
57

Other Iteration Methods
Using the same pattern as Hash.each, you can use these other iteration
methods. As with Hash.each, each method here iterates over each member
in the hash, applying the passed-in function to each member and passing
that function the value and the key for each one. They also take a second,
optional, argument for binding.
Hash.filter: This method returns a new Hash excluding any item for
which the method passed to filter returns something “falsy” (zero, empty
string, null, undefined, or false).
var evens = $H({
a: 1, b: 2, c: 3
}).filter(function(value, key){
return !(value % 2);
}); //evens = Hash({b: 2});
Hash.some: This method returns a Boolean—true if the method passed to
some returns true at least once. Note that you don’t have to declare the key
in the passed function if you don’t use it.
var oneIsEven = $H({
a: 1, b: 3, c: 5
}).some(function(value) {
return value % 2 == 0;
}); //Returns false, because 1,3,5 are each not even
Hash.every: This method returns a Boolean—true if the method passed to
every returns true for each item in the hash.
var greaterThanOne = function(value){return value > 1};
var lessThanFive = function(value) {return value < 5};
$H({a: 1, b: 2, c:3}).every(greaterThanOne);
//Returns false
$H({a: 1, b: 2, c:3}).every(lessThanFive);
//Returns true
58
MooTools Essentials

Hash.map: This method returns a new hash—the result of the returned
values for the method passed to map.
var timesTwo = function(value){
return value*2;
};
var twoFourSix = $H({a: 1, b: 2, c: 3}).map(timesTwo);
//twoFourSix = Hash({a: 2, b: 4, c: 6});
var timesThree = $H({
a: 1, b: 2, c: 3
}).map(function(value, index){
return value*3
});
//timesThree = Hash({a: 3, b: 6, c: 9});
Hash :: Introspection Methods
Hash provides methods to retrieve information about the data in the hash
that should be used instead of the dot notation or bracket notation used in
native objects.
var ninja = {color: "black", side: "evil"};
ninja.color = "red";
//This is OK for native objects of course
var ninjaHash = new Hash(ninja);
ninjaHash.get('color') ;
//Returns "red"
Hash.get: This method returns the value for the given key.
$H({apple: 'red', lemon: 'yellow'}).get("apple");
//Returns 'red'
$H({apple: 'red', lemon: 'yellow'}).get("grape");
//Returns undefined

MooTools Essentials
59

Note
Hash.get does not retrieve properties of Hash—only the
properties of the object you pass in to Hash. So, for example, although
Hash has the method each, invoking $H({foo: bar}).get('each')
would return null; this is because each is not a member of {foo:bar}—
it’s a member of Hash. Hash wraps your object with its own methods, but it
treats your object as if Hash has not altered it.
Hash.getClean: This method returns an object that has none of the hash
methods.
$H({apple: 'red', lemon: 'yellow'}).getClean;
//Returns {apple: 'red', lemon: 'yellow'}
Hash.getKeys: This method returns an array of all the keys in the hash.
$H({apple: 'red', lemon: 'yellow'}).getKeys();
//Returns ["apple", "lemon"]
Hash.getLength: This method returns the length of the number of
key/value objects in the hash.
$H({apple: 'red', lemon: 'yellow'}).getLength();
//Returns 2
Hash.getValues: This method returns an array of all the keys in the hash.
$H({apple: 'red', lemon: 'yellow'}).getValues();
//Returns ['red', 'yellow']
Hash.has: This method returns true if the hash has a value for the
specified key.
$H({apple: 'red', lemon: 'yellow'}).has('grape');
//Returns false
$H({apple: 'red', lemon: 'yellow'}).has('apple');
//Returns true
60
MooTools Essentials

Hash.hasValue: This method returns true if the hash contains the
specified value.
$H({apple: 'red', lemon: 'yellow'}).has('red');
//Returns true
$H({apple: 'red', lemon: 'yellow'}).has('purple');
// Returns false
Hash.keyOf: This method returns the corresponding key for a given value if
the hash contains that value.
$H({apple: 'red', lemon: 'yellow'}).keyOf('red');
//Returns 'apple'
$H({apple: 'red', lemon: 'yellow'}).keyOf('purple');
//Undefined
Hash.toQueryString: This method returns a query string of key/value
pairs for all the contents of the hash. Note that this really only works if the
toString method of the values returns a useful notation of the object. So,
for instance, if one of the values in your hash is a DOM element, the
toString representation of that is not likely to be useful. Booleans, strings,
numbers, and arrays are more likely to be useful with this method.
$H({apple: 'red', lemon: 'yellow'}).toQueryString();
//Returns apple=red&lemon=yellow
Hash :: Manipulation Methods
Hash has several methods that allow you to alter the contents of the hash
itself.
Hash.empty: This method removes all key/value pairs from the object.
$H({apple: 'red', lemon: 'yellow'}).empty();
//Hash no longer has any keys/values
Hash.erase: This method removes a specific key/value pair (pass in the
key).
$H({apple: 'red', lemon: 'yellow'}).erase('apple');
//Hash is now {lemon: 'yellow'}

MooTools Essentials
61

Hash.extend: This method adds all the key/values for the object passed in,
overwriting any namespace collisions. This is the equivalent syntax for
$extend(obj1, obj2).
$H({
apple: 'red', lemon: 'yellow'
}).extend({apple: 'green'});
//Hash is now {apple: 'green', lemon: 'yellow'}
Hash.include: This method adds the key/value set if the key is not already
present.
$H({
apple: 'red', lemon: 'yellow'
}).include('apple', 'green');
//Hash is now {apple: 'red', lemon: 'yellow'};
Hash.combine: This method adds all the key/values for the object passed
in, excluding any namespace collisions.
$H({apple: 'red', lemon: 'yellow'}).combine({
apple: 'green', grape: 'purple'
});
//Hash is now
//{apple: 'red', lemon: 'yellow', grape: 'purple'}
Hash.set: This method sets the value for the given key.
$H({
apple: 'red', lemon: 'yellow'
}).set('apple', 'green');
//Hash({apple: 'green', lemon: 'yellow');
Functions
At the heart of modern JavaScript is the concept of functional
programming (see “Functional Programming (a.k.a. Lambda)” in the
Appendix). Unfortunately, there are a lot of things that you’ll likely want to
accomplish with functions that the native JavaScript specification makes
62
MooTools Essentials

far from simple. Thankfully, MooTools makes most of these tasks easier to
accomplish.
Function Methods Generate Copies
As with most native objects, MooTools adds methods to the Function
prototype. This makes these methods available on all functions. It’s
important to note that executing most of these methods returns a new
function (some of them return the result of invoking the function, like $try
or .call). The new function is the same as the old one, except some new
attribute has been defined for this new one, but it’s not the same function—
it’s a copy of it.
This distinction is important to keep in mind whenever you have a pointer
to a function and you need to reference it again.
An example here requires that I jump ahead a bit, but I think it’s important,
so bear with me. Consider adding an event to a DOM element (this is
MooTools syntax):
var highlight = function(){
this.setStyle('background-color', 'yellow'
});
$('myElement').addEvent('click',
highlight.bind($('myElement').getParent())
);
//...Later
$('myElement').removeEvent('click', highlight);
//This won't work!
Allow me to explain the preceding code. It contains a method that will
change the background color of an element to yellow. It references the
keyword this, meaning that you expect an element to be bound to the
function (see “‘this’ and Binding” in the Appendix). Then you attach an
event to an element, but you bind the highlight method to the parent of
your element because you want to highlight that. Later you decide to

MooTools Essentials
63

remove that event. removeEvent takes as its argument the event (click)
and the function you attached previously (highlight).
But wait! This won’t work! Why? Because when you called bind on
highlight when you attached the event, what was attached was a copy of
highlight—a copy with its bind property set.
So how do you manage this kind of scenario? You have to keep a reference
to the new copy:
var highlight = function(){
this.setStyle('background-color', 'yellow')
};
var parentHighlight =
highlight.bind($('myElement').getParent());
$('myElement').addEvent('click', parentHighlight);
//...Later
$('myElement').removeEvent('click', parentHighlight);
//voila!
This pattern isn’t one you’ll encounter a lot—needing to keep a reference
like this—but it’s very important to recognize that when you call a method
on a function, it usually returns a copy of the function. The methods that do
not return a copy like this are the methods that return something other than
the function—like attempt, which returns the result of the function or
null if the attempt fails.
Function.attempt
This executes the function and returns the value that the function returns
unless there is an exception, in which case it returns null; however, the
exception is not raised to the browser. This takes an optional second
argument for a bind object (see Function.bind next).
64
MooTools Essentials

//And here it is passing in more than one argument
var highlight = function(color, border) {
this.setStyles({
'background-color': color,
'border-color': border
});
};
var boundHighlight =
highlight.bind($('myElement'), ['red', 'green']);
boundHighlight();
At this point, you are no doubt asking yourself why you would ever write
JavaScript this way. The reality is that you wouldn’t in all likelihood. I’m
trying to illustrate the concept of binding here so that when you get into the
examples in the next section of the book, it’ll be clear to you.
But to put it in perspective, by writing code this way, it is possible to write
very abstract methods and collections of methods that can be reused in
many, many different ways. Indeed, all you have to do is look through
MooTools itself to see all of these concepts in action (see “‘this’ and
Binding” in the Appendix for more details on binding).
Function.bindWithEvent
You probably won’t find yourself using this very often, but it does
sometimes come in handy. Here’s what appears in the MooTools
documentation: “Changes the scope of this within the target function to
refer to the bind parameter. It also makes ‘space’ for an event. This allows
the function to be used in conjunction with Element.addEvent and
arguments.” Here’s the syntax:
myFunction.bindWithEvent(bind, arguments);
//arguments are optional
66
MooTools Essentials

And here’s an example:
function myFunc(event, add){
//Note that 'this' here refers to the current
//scope, typically the window, not an element.
//We'll need to bind this function to the
//element we want to alter.
this.setStyle('top', event.client.x + add);
};
$(myElement).addEvent('click',
myFunc.bindWithEvent(myElement, 100);
//When clicked, the element will move to the
//position of the mouse + 100.
The reason you won’t use it very often is because you’ll typically work
with events via the element method addEvent, which automatically does
all this for you.
Function.delay
This method delays the function, executing it after the given duration
specified. This method returns the JavaScript timeout ID, which can be
used to cancel the call. This takes as optional arguments bind and
arguments; see the discussion on function.bind earlier in the chapter
for more on these arguments.
var hilight = function(color){
this.setStyle('background-color', color);
};
var hilightDelay =
highlight.delay(500, $('myElement'), 'red');
//Wait 500ms, then execute highlight, passing 'red'
//as its argument binding $('myElement') to
//the function
$clear(hilightDelay); //Nevermind!

MooTools Essentials
67

Function.pass
This method will create a copy of a function with its arguments already
specified (to be executed later). The second argument for binding is
optional (see the discussion on function.bind earlier).
var say = function(msg){
alert(msg.toString());
return true;
};
var howdy = say.pass('howdy');
//...Later
howdy(); //Alerts "howdy"
Function.periodical
This method works just like function.delay, except that it recurs.
var blink = function(){
if (this.getStyle('display') == 'none')
this.setStyle('display', 'block');
else this.setStyle('display', 'none');
};
blink.periodical(500, $('myElement'));
//Egads! The blink tag is back!
Function.run
JavaScript has its own native methods to execute a function while binding
something to it at the same time: Function.apply and Function.call.
Those methods take as arguments the this keyword to bind to the function
and a second, optional list of arguments to pass to the function. The
difference between them is that call takes a single argument, while apply
takes an array.
68
MooTools Essentials

For example:
var highlight = function(color){
this.setStyle('background-color', color);
};
highlight.apply($('myElement'), ['yellow']);
//Same as
highlight.call($('myElement'), 'yellow');
This is handy if you need to bind something to a function before you
execute it. Otherwise, you’d have to do something silly like this:
highlight.bind($('myElement'), 'yellow')();
What if you want to just run a method and pass arguments to it but not
necessarily bind anything to it? What if you want to call a function and
pass it an array of arguments? It’s ugly to pass null values in for the bind
argument just to be able to pass an array to the function:
var say = function(name, msg){
alert(name + ' says ' + msg);
};
var words = ['bob','hi'];
say.apply(null, words);
//We don't need to bind anything,
//but passing null is kinda ugly
So MooTools gives you function.run, which takes as its first argument
an array or a single object to pass to the function, and the bind argument is
optional.
var say = function(msg){ alert(msg); };
var talk = function(){
$A(arguments).each(say);
};
talk('I', 'like', 'cheese'); //Alerts each argument
var msgs = ['I', 'like', 'cheese'];
talk.run(msgs);

MooTools Essentials
69

OK, why not just pass the arguments straight to the function—why would
you want to pass an array of arguments? Well, sometimes you are getting
values programmatically, and you have the arguments for a function as a
reference to an array or a string or whatever. You can throw any of these
things at run, and it’ll handle it.
Numbers
Most of the native methods for Number in JavaScript are part of the Math
object or are stand-alone functions. For example, parseInt is just a built-
in function to parse a string to an integer.
This isn’t a very MooTools way of doing things though; MooTools prefers
to add methods to the prototypes of natives, so MooTools translates most
of these as methods on Number.
As a result, most of the MooTools methods for Number are native methods
just applied to the numbers as methods.
var x = 3.5;
x.floor(); //Returns 3
Math.floor(3.5); //Same thing
Note that you can’t execute these methods on the literal for numbers
(because number literals can contain decimals), so this won’t work:
3.floor();
But this would:
(3).floor();
In addition to converting all the Math methods (abs, acos, asin, atan,
atan2, ceil, cos, exp, floor, log, max, min, pow, sin, sqrt, and tan) to
native methods, MooTools adds the following methods:
70
MooTools Essentials

Number.limit: This method limits the number between two bounds.
(12).limit(2, 6.5); //Returns 6.5
(-4).limit(2, 6.5); //Returns 2
(4.3).limit(2, 6.5); //Returns 4.3
Number.round: This method rounds a number to a given precision.
(12.45).round() //Returns 12
(12.45).round(1) //Returns 12.5
(12.45).round(-1) //Returns 10
Number.times: This method iterates a method a given number of times,
passing as the argument the number of the current iteration. It also takes an
optional second argument for binding.
(4).times(alert);
//Alerts "0", then "1", then "2", then "3".
In many ways, this is just a shortcut for a standard for loop, but it also
conforms to that notion of functional programming discussed elsewhere in
this book.
Number.toFloat: This method returns a number as a float. This is useful
because sometimes you have a value and you may not know whether it’s a
string or a number (for example, Element.setStyle takes for the
numerical property of CSS values either a number or a string).
(111).toFloat(); //Returns 111
(111.1).toFloat(); //Returns 111.1
Number.toInt: Much like Number.toFloat, this is useful when you have
a variable that may be a number or a string. It takes as an optional argument a
base value that defaults to 10. This is an important distinction to the native
parseInt, which also defaults to 10 unless the string you pass it starts with
a zero; in that case, it switches to octal for the radix so that parseInt(012)
returns 10 (awesome!), unless you pass it a second argument to explicitly tell
it to use base 10, as it would otherwise . . . But I digress. MooTools adds
Number.toInt and makes this all better.

MooTools Essentials
71

"111".toInt(); //Returns 111
(111.1).toInt(); //Returns 111
"012".toInt(); //Returns 12
//You can specify a different base; this returns 7:
"111".toInt(2);
Strings
Strings in MooTools get several methods that fall into two basic camps:
introspection and manipulation (the bulk of them are in the latter):
METHOD TYPE
METHOD NAME
Introspection
contains, test
Manipulation
capitalize, camelCase, clean, escapeRegExp,
hyphenate, stripScripts, substitute,
toFloat, toInt, trim
Less commonly used hexToRgb, rgbToHex
String.contains: This method checks to see whether the string contains
the passed-in string. You can pass in a second argument, which it will use to
separate the string into chunks, and then compare each of those to the one
you’re looking for.
'a bc'.contains('bc'); //Returns true
'a b c'.contains('c', ' '); //Returns true
'a bc'.contains('b', ' '); //Returns false
String.test: This method checks to see whether a string passes a regular
expression; it returns true or false. You can pass a second argument for
RegExp options. Alternatively, you can pass in a RegExp object.
"I like cookies".test("cookie"); //Returns true
"I like cookies".test("COOKIE", "i");
//Returns true (ignore case)
"I like cookies".test(/COOKIE/i); //Same as above
"I like cookies".test("cake"); //Returns false
72
MooTools Essentials

String.toFloat, String.toInt: These methods convert a value to a
float or an integer.
"3".toInt(); //Returns 3
"3.4".toInt(); //Returns 3
"3.4".toFloat(); //Returns 3.4
String.camelCase, String.hyphenate: These two methods convert
strings between each other.
"borderTop".hyphenate(); //Returns "border-top"
"border-top".camelCase(); //Returns "borderTop"
String.capitalize: This method capitalizes the first letter of each word.
"i like cookies".toInt(); //Returns I Like Cookies
String.trim, String.clean: This method removes whitespace at the
beginning and end of a string; clean also removes line breaks.
" i like cookies \n\n".clean();
//Returns "i like cookies"
String.escapeRegExp: This method escapes the characters in a string that
would otherwise mess up a regular expression.
'animals.sheep[1]'.escapeRegExp();
//Returns 'animals\.sheep\[1\]'
String.stripScripts: This method removes all <script> tags from a
string of HTML; you can optionally pass in true as the argument to evaluate
those scripts before removing them.
String.substitute: This method substitutes keywords in a string using
an object of key/values. You can optionally pass in a RegExp as the second
argument to denote the pattern used to match the keys. The default for this is
/\?{([^}]+)}/g, which translates to “{key}”.

MooTools Essentials
73

Event Methods
Events only have three methods, and they all basically in some way or
another obstruct the event from processing the way it normally would. To
understand this requires knowledge of how DOM events are handled by
browsers.
When an event fires on a DOM element, in some circumstances two
primary things occur: the default behavior (clicking a link takes you to
another page, clicking the submit button submits the form) and also
propagation. Propagation occurs when you click (or mouseover, keydown,
etc.) an element inside another element. The browser fires the click event
for both elements, which makes sense, if you think about it: if you click a
box inside a box, the browser doesn’t really know which one you’re really
clicking—you’re clicking both—so it fires the onclick event of the
innermost element, and then its parent, and on up to the document.
MooTools provide methods to stop either or both of these actions:
Event.preventDefault: This prevents the default behavior from
occurring.
$('myCheckbox').addEvent('click', function(event){
event.preventDefault();
//Will prevent the check box from being "checked".
});
Here the check box won’t get checked, but if there’s any other click behavior
on this element or any of its parents, those events will fire.
Element.stopPropagation: This method prevents the events that fire on
the parents of an element. For example, clicking an element will fire the
onclick event for that element, and then the onclick event for its parent,
and its parent’s parent, and so on. Element.stopPropagation prevents
these events from firing on the parents.

MooTools Essentials
75

$('myElement').addEvent('click', function(){
alert('click');
return false;
//Equivalent to stopPropagation and preventDefault.
});
$('myChild').addEvent('click', function(event){
event.stopPropagation();
//This will prevent the event from bubbling up,
//and so that the parent's click event won't fire.
});
Element.stop: This is the method I use 99% of the time. It basically stops
both the propagation of the event and the default behavior.
HTML:
JavaScript:
$('myAnchor').addEvent('click', function(event){
event.stop();
//Prevents the browser from following the link.
this.setText("Where do you think you're going?");
//'this' is Element that fires the Event.
});
Event Properties
In addition to the methods to prevent events from continuing, the Event
object contains data about the event.
  shift: (Boolean) true if the user pressed the Shift key.
  control: (Boolean) true if the user pressed the Ctrl key.
  alt: (Boolean) true if the user pressed the Alt key.
  meta: (Boolean) true if the user pressed the meta key.
  wheel: (Integer) The amount of third button scrolling.
76
MooTools Essentials

  code: (Integer) The keycode of the key pressed.
  page.x: (Integer) The x position of the mouse, relative to the full window.
  page.y: (Integer) The y position of the mouse, relative to the full window.
  client.x: (Integer) The x position of the mouse, relative to the viewport.
  client.y: (Integer) The y position of the mouse, relative to the viewport.
  key: (String) The key pressed as a lowercase string. key can be “enter”,
“up”, “down”, “left”, “right”, “space”, “backspace”, “delete”, “esc”, “a”, “b”,
“c”, “d”, and so on.
  target: (Element) The event target, not extended with $ for performance
reasons.
  relatedTarget: (Element) The event-related target, not extended with $.
The data about the event can let you author complex interactions, like using
Ctrl+S to save a form or altering a CSS property for a DOM element when
users scroll their mousewheel.

MooTools Essentials
  77

Chapter 5: Elements
Browsers implement what is known as the DOM—the Document Object
Model. JavaScript as a language isn’t indigenous to browsers nor limited to
them, it’s just that the browsers are where developers typically use
JavaScript. But the browsers themselves extend the basic language to add
methods and properties to JavaScript objects that relate to HTML tags
rendered to the viewer.
This relationship between the JavaScript world and the HTML world is the
DOM. With the DOM comes numerous methods that only make sense in a
browser, and most of these are methods on Element, the JavaScript object
that relates to HTML tags in the page. The methods that are natively part of
Element, much like other native JavaScript methods, leave something to
be desired. Often they seem overly verbose or explicit, while other times
they seem woefully insufficient to allow for the authoring of clean code.
At its heart, MooTools really makes two things its priority: first, it strives
to make writing object-oriented, reusable, and cleanly readable JavaScript
an easy thing to do, and second, it strives to make interactive web pages
easy to author. Consequently, MooTools gives a lot of attention to the
Element native, adding many, many methods that allow you to write clean,
legible, expressive code.
Creating and Cloning Elements
MooTools makes the task of creating an element much easier than native
JavaScript, offering up a syntax that feels much like that for instantiating a
class:

MooTools Essentials
79

If you need to also clone events, that’s a different method entirely (in
Element/Element.Events.js):
var myCopy = myElement.clone();
//Clone the click events
myCopy.cloneEvents(myElement, 'click');
//Clone all of the events
myCopy.cloneEvents(myElement);
Of course, creating and injecting elements into the DOM is only a small
part of the picture. You’re much more likely to write most of your HTML
the old fashioned way, and that means you must collect the elements from
the document somehow.
Collecting Elements from the DOM
MooTools contains three shortcuts for collecting elements from the DOM:
$, $$, and $E.
$ :: Element/Element.js
What it does: Collects an element from the DOM by ID.
Usage:
$('myElementId');
Example:
$('ninja').setStyle('visibility', 'hidden');
When you’ll use it: The $ function has two main purposes:
  Serves as a shortcut for document.getElementById, which we can all
agree is so many keystrokes that it’s just cruel considering how often we need
to perform the task
  Initializes element objects with MooTools
While it’s possible to still collect elements by ID using the standard method
(document.getElementById), it’s a bad practice to use it when using

MooTools Essentials
  81

MooTools for a couple reasons: it’s just more characters than using the
MooTools method ($), and MooTools ensures that the element returned has
had the MooTools element methods applied to it (see the next section).
Also note that any of the DOM collection methods
(Element.getElements, for example) will initialize the elements
returned.
Using $ to Ensure You Have an Initialized Element
This function is also useful when you aren’t sure whether the value you
have is a reference to an element or its ID, or if you are unsure whether that
element has already been initialized for MooTools. For example, if you
have a method or a function that accepts an element as an argument, the
user might pass you an ID, an initialized element, or an element that hasn’t
yet been initialized. You can use $ as a quick way to ensure that you get an
initialized element.
If you pass an argument to $ that is not an ID of an element in the DOM or
isn’t an element reference, it returns null, so it’s also useful to check
whether the ID of an element is found in the DOM or not. Consider the
following demonstration:
function hideNinja(element) {
element = $(element);
if (element) element.setStyle('visibility', 'hidden');
};
In this example, the user could pass an ID (a string), an element that was
collected already using $, or an element collected using non-MooTools
means (document.getElementById). The $ function will return the
initialized element or false if it can’t locate the element in the DOM (if
it’s passed an ID; if you pass it an element, the element doesn’t have to be
in the DOM yet).
82
MooTools Essentials

Using $ on an Element that’s already been initialized does not have any ill
effects or costs.
$$ :: Element/Element.js
What it does: Returns a collection of elements that match the passed-in
selector.
Usage:
$$('div'); //All the divs in the DOM
$$('a', 'b'); //All the anchor & bold elements
Note Using
$$ with more than one selector will return a collection with
the results of each selector grouped (so $$('a', 'b') will be a collection
with all the links followed by all the bold elements).
Example:
$$('div.ninja').each(function(ninja){
ninja.setStyle('visibility', 'hidden');
});
When you’ll use it: $$ collects all the elements that match a given selector
and returns them as an array of elements that also has all the Element
methods applied that MooTools refers to as an elements collection. If $$
does not find any elements that match the selector, it returns an empty
collection (an empty array).
By default, you can only pass tag names (div, b, a, etc.) to $$, but when
you include Selectors/Selectors.js, $$ will also take richer CSS path
expressions (e.g., div.someClass a#someId—see “Selectors” in Chapter
6).
When $$ doesn’t find any matching elements for a selector, it returns an
empty array.

MooTools Essentials
83

Element Methods and Collections
When you create a collection, all the Element methods are applied to it; for
example, Element.setStyle can be used with an elements collection.
$$('div.ninjas').setStyle('visibility', 'hidden');
//Hide all the ninjas
When you execute an Element method on an element collection,
MooTools iterates over the collection and executes the method on each
one. While it’s possible to chain these methods, it’s bad form because you
would iterate over the collection twice. For example:
//This is bad
$$('div.ninja').setStyle('visibility',
'hidden').addClass('invisible');

//It's the equivalent of the following
$$('div.ninjas').each(function(ninja){
ninja.setStyle('visibility','hidden');
}).each(function(ninja){
ninja.addClass('invisible');
});

//This is better; you only iterate once
$$('div.ninjas').each(function(ninja){
ninja.setStyle('visibility',
'hidden').addClass('invisible');
});
MooTools has numerous methods for collecting a group of elements from
the DOM, but $$ is the only stand-alone function. Other methods are
attached to Element prototypes. Element.getElement,
Element.getElements, Element.getChildren, and others allow for
element collection, too.
84
MooTools Essentials

$E :: Element/Element.js
What it does: Returns the first element that matches the passed-in selector.
Usage:
//The first div in the DOM:
$E('div');
//The first link or, if no links are found,
//the first bold tag:
$E('a', 'b');
Example:
$E('div.ninja').setStyle('visibility', 'hidden');
When you’ll use it: Much like $, it’s a useful shortcut: $E is the equivalent
of $$(selector)[0]. When $E does not find a match for the given
selector, it returns null.
Note
$E was left out of MooTools 1.2, but has been re-added for the
next release. I use this method a lot, so I’m leaving this in here because it
will be useful again soon. In the mean time, if you want to use this method,
just add this to your own code:
$E = document.getElement.bind(document);
Element Methods for Collecting Children, Siblings,
and Parents
In addition to $, $$, and $E, which allow you to collect elements from the
entire document, you can use methods attached to Element by MooTools
that help you select specific child elements. These work mostly like the
preceding methods, except that they only select children of the element on
which they are run.

MooTools Essentials
85

Element.getElement: This method works just like $E; pass it a selector,
and it returns the first child to match it.
$('myElement').getElement('div');
//Returns the first div inside myElement
Element.getElements: This method works similarly to $$; pass it a
selector, and it returns a collection of children of the element that match it.
$('myElement').getElements('div');
//Returns the all divs inside myElement
Element.getElementById: This method works just like $; pass it an ID,
and it returns the first child to match it.
$('myElement').getElementById('myChildElement');
//Returns the first element inside myElement
//with ID 'myChildElement'. This is the same
//as the following, which is the preferred method
$('myElement').getElement('#myChildElement');
//Note the '#'
Element.getChildren, Element.getChild: These methods work like
getElement and getElements (you can pass these an optional selector)
but are limited to direct children of the element.
Element.getParent, Element.getParents: These methods work just
like getChildren and getChild (you can pass an optional selector). If you
pass a selector to getParent, it will flow up through the DOM, inspecting
each parent to find a match; otherwise, if you don’t specify a selector, it
returns the immediate parent of the element. getParents does the same but
returns all the parents that match the selector (or, if no selector is specified,
all the parents up to the document root).
Element.getNext, Element.getAllNext, Element.getPrevious,
Element.getAllPrevious: These methods work like getChild and
getChildren, returning the first sibling to match the selector (for getNext;
getPrevious obviously gets the previous sibling), or an array of siblings
for the “All” methods.
86
MooTools Essentials

Element.hasChild: This method returns true if the specified element is a
child (of any depth, so it can be a child of a child, for example).
myElement.hasChild(kid);
//Returns true if myElement contains kid
Setting, Getting, and Erasing Properties of Elements
The JavaScript representation of an element provides both methods and
attributes. Attributes of an element can be referenced using dot or bracket
notation:
myImg.src = "/foo.jpg";
myImg[“src”] = "/foo.jpg";
This method of setting a property is technically deprecated. The current
specification for setting an attribute is to use the setAttribute method,
and for getting one you have getAttribute:
myImg.setAttribute('src', '/foo.jpg');
myImg.getAttribute('src'); //Returns '/foo.jpg'
This is a more functional approach to managing attributes, but it isn’t well
implemented across all the browsers. MooTools takes this and adds a lot
more options and functionality, using the shorter set and get and adding
into the mix the method erase, which lets you remove an attribute entirely.
Element.set
What it does: Sets an attribute of an element to a specified value.
Usage:
Element.set(property, value);
Example:
myImg.set('src', 'foo.jpg');

MooTools Essentials
87

In addition to being able to get or set any attribute, you can also do things
like set the innerHTML of an element:
myDiv.set('html', '<b>new html!</b>');
In native JavaScript, you’d be forced to do the following:
myDiv.innerHTML = '<b>new html</b>';
What’s so bad about that? Well, in addition to not being a method (which
you could delay or bind, for instance), it has cross-browser issues
(attributes sometimes have different names in different browsers, and you
can’t use it to set every attribute as you would think you could). set and
get solve these issues for you, providing a much more friendly interface to
element attributes.
set has more powerful capabilities than just specifying a single attribute.
For instance, you can also pass it an object of values:
myImg.set({
src: '/foo.jpg',
alt: 'this is foo',
//Class is a reserved word in JS,
//so we must use quotes
'class': 'fooClass',
//In addition to standard attributes, you can also
//use set for some special attributes defined by
//MooTools
events: {
click: function(){ alert('click!');}
},
styles: {
border: '1px solid blue',
marginTop: '10px'
},
etc...
});
88
MooTools Essentials

When you’ll use it: Any time you want to set an attribute on an element,
you should use set. Note that MooTools has a few other Element methods
(like setStyle) that allow you to set some specific properties. You can
still use set for these if you prefer.
myElement.setStyle('border', '1px solid blue');
myElement.set('styles', {border: '1px solid blue'});
//Same result
Element.get
What it does: Allows for custom functionality, which MooTools uses to
create shortcuts that are useful, but you can use them, too. MooTools adds
things like get('value'), which returns the value of an input or text area.
The attributes that MooTools provides special access to are html, href,
text, value, and tag, as well as shortcuts to effects (more in Chapter 9).
Usage:
myElement.get(property);
Example:
myInput.get('value');
myImage.get('src');
When you’ll use it: The get method allows you to inspect an element for
various attributes, and in general you should always use it to do so. As
noted with set, there are some methods (like getStyle) that MooTools
provides its own methods for which are the preferred methods for
retrieving that information.
Element.erase
What it does: Removes an attribute value altogether.
Usage:
myElement.erase(property);

MooTools Essentials
89

Example:
myImg.erase('alt');
When you’ll use it: Sometimes (though I find somewhat rarely), you want
to remove a property altogether. If you have a method that checks for an
attribute on an element and performs an action based on the result, for
example, then you need to remove the attribute—not just set it to some
nonactive value (like an empty string).
Custom Getters and Setters and Erasers
MooTools allows you to define your own methodology for a get, set, and
erase routine. This can be useful if you find you repeatedly need to process
some attribute of an element. You can make a method and implement it
into Element (see “Native.implement” in Chapter 4), or you could create
your own custom getter and setter.
Say that you wanted to add a new attribute, get/set('yellow'). You
could implement this yourself:
Element.Properties.yellow = {
set: function(){
return this.setStyle('background-color', 'yellow');
},
get: function(){
return this.getStyle('background-color')=='yellow';
},
erase: function(){
return this.setStyle('background-color', 'inherit');
}
};
myDiv.set('yellow'); //It's yellow
myDiv.get('yellow'); //Returns true
In this way, MooTools allows you to define your own attributes and their
meaning, much as it lets you extend native objects with new attributes and
90
MooTools Essentials

methods. It’s a very powerful way to extend the environment to suit your
needs. It’s especially useful if you have a widget or effect that requires an
element to work.
Element Injection and Removal
What they do: Either manipulate the content of the DOM (inject, adopt,
wraps, grab, and replaces) or remove elements or their contents
(dispose, empty, and destroy).
When you’ll use them: Selecting and creating elements is just the tip of
the iceberg with what you can do with them, but it won’t do you any good
if they aren’t in the DOM (as they are when you create a new element—it’s
not part of the document until you inject it) or if they’re in the wrong place.
The MooTools documentation is pretty straightforward on how to use these
methods, but here’s a quick rundown of them:
Element.inject: This method inserts or moves an element into the DOM
at the specified location. The default placement is "bottom", meaning that it
will inject the element into the specified parent as the last child of that parent.
Other options include "before", "after", and "top".
myElement.inject(newParentElement);
//myElement is now the last child of newParentElement

myElement.inject(siblingElement, "before");
//myElement is now inside the same parent
//as siblingElement
//and is previous to that sibling
Element.grab: This method is just like inject, only in reverse—the
passed-in argument is injected into the element invoking the method. The
second, optional argument can be either "top" or "bottom" (the default).

MooTools Essentials
91

newParentElement.grab(myElement);
//myElement is the last child of newParentElement
newParentElement.grab(myElement, "top");
//myElement is the first child of newParentElement
Element.adopt: This method is just like grab, except it allows multiple
elements to be adopted, which are always at the bottom.
newParentElement.adopt(myElement, myOtherElement, etc);
Element.wraps: This method is just like grab, except instead of moving
the target into the parent, it moves the parent to be around the target. The
parent of the target becomes the parent of the element grabbing the target, and
the target becomes a child of the element doing the grabbing. You can pass an
optional second argument for where the child should be put into the new
parent—either 'top' or 'bottom'.
oldParent.grab(myElement);
//oldParent now has myElement as a child
newParent.wraps(myElement, 'top'); //top is optional
//newParent is now a child of oldParent
//and myElement is now a child of newParent
Element.replaces: This method removes the specified element and puts a
new one in its place.
myNewElement.replaces(myOldElement);
Element.empty: This method removes all the child nodes from the element
using the Element.destroy method.
Element.dispose: This method removes the element from the document,
but NOT from memory. This means you could inject it back into the DOM
later if you wanted.
92
MooTools Essentials

Element.destroy: This method removes the element from the document
entirely and collects its memory. This means you CANNOT inject it back
into the DOM later if you wanted. This is useful if you’re managing a lot of
content on a page and you need to reclaim the memory (for instance, you
have an image gallery where you only want to keep 50 images in memory at a
time).
Element (CSS) Classes
You can easily add and remove classes to an element and also find out
whether one is already there. These are fairly self explanatory.
myElement.addClass('blue');
myElement.hasClass('blue'); //Returns true
myElement.removeClass('blue'); //No more blue
myElement.toggleClass('blue'); //Blue again
myElement.toggleClass('blue'); //No more blue (again)
Element Storage
This is perhaps one of the coolest things in MooTools, if you ask me.
Simply put, element storage is the ability to store anything in JavaScript
(an object, function, value, class, another element, whatever) as an attribute
of an element.
You can technically do this natively like so:
var myFoo = new Foo();
myElement.foo = myFoo;
The problem with it is that it tends to leak memory when you reference
certain types of objects (basically, anything except a string or a number). A
lot. So it’s considered very bad form—irresponsible even—to store data
this way.
awesome explanation, and rather than rewrite it all, I’m going to just quote
it because it explains it so well:

MooTools Essentials
93

What’s New in 1.2: Element Storage
Jan. 22, 2008, Tom Occhino
When developing advanced JavaScript applications, it’s sometimes
beneficial to associate extra properties or attributes to DOM elements.
While we have always been able to use DOM elements as storage
containers for all sorts of other data, this generic technique has a few
drawbacks. While the problems associated with this technique are almost
exclusively Internet Explorer problems, they must be dealt with
nonetheless.
Let’s consider the following simple example:
var element = $('myElement');
element.effectInstance = new Fx.Tween(element, 'color');
element.customProperty = 'someProperty';
element.effectInstance; //The Fx.Tween instance
element.customProperty; //'someProperty'
As we know, IE doesn’t like when objects are stored as Element attributes
in this way, and the effectInstance property will leak if it’s not
manually managed. Another problem we’ve seen is that when accessing the
innerHTML of any parent of our element, IE will return simple custom
properties (like strings, numbers, etc.) along with the expected properties.
This means that customProperty would be copied as well, which could
pose a problem if it was some unique custom attribute. Obviously, of the
two cases, memory management is our biggest concern here, but both are
issues to consider.
94
MooTools Essentials

A MooTools-Worthy Solution
Element.Storage is brand new in MooTools 1.2. It is basically an
external Hash that stores all the custom properties and events for every
element you interact with.
Let’s take another look at our previous example, this time using the new
Element.Storage API:
var element = $('myElement');
element.store('effectInstance',
new Fx.Tween(element, 'color'));
element.store('customProperty', 'someProperty');
element.retrieve('effectInstance');
//The Fx.Tween instance
element.retrieve('customProperty'); //'someProperty'
Note that events and actions are no longer attached directly to the elements.
Everything is stored in the external Hash and managed by MooTools, so as
a developer, you have nothing to worry about. Finally, an elegant and
coherent API for attaching custom properties, functions, and objects to
elements.
Advanced Examples
Element:retrieve actually accepts an optional second parameter that
will act as the default value to store if another value doesn’t previously
exist. It will then retrieve the value as expected.
$('myElement').retrieve('defaultValue',
'Some Default Value');
//Stores and returns 'Some Default Value'
//if the key doesn't previously exist
Also, many users have asked about namespacing the element storage. We
have responded by telling them that it already allows this since you can
store objects and hashes. Consider the following example:

MooTools Essentials
95

var element = $('myElement');
var data = element.retrieve('galleryData', {});
data.id = 16;
data.source = '/images/16.jpg';
data.title = 'Some Title';
//Later
$('myElement').retrieve('galleryData');
//{ id: 16, source: '/images/16.jpg',
// title: 'Some Title' }
$('myElement').retrieve('galleryData').id; //16
The Elements Object
In addition to the native Element object, MooTools has a special type of
array of elements called Elements (also referred to as a collection in this
book). I outline the basic principal of the Elements object in the section
“$$ :: Element/Element.js” earlier in the chapter.
Any time you collect a group of elements from the DOM, you’ll be using
one of these Elements objects.
Elements Methods
The Elements object is an array of elements that has all the properties of
Array plus all the methods of Element. So, for example, indexOf (an
Array method) works:
$$('div').indexOf(myDiv);
And so does set, an Element method:
$$('img').set('src', '/foo.jpg');
//All the images' sources are /foo.jpg now
As I pointed out in the section “$$ :: Element/Element.js,” it’s important to
realize that this shortcut iterates over all the elements in the collection and
executes the element method on each. Therefore, it’s inefficient (and bad
form) to chain these methods (quoting from the $$ example earlier):
96
MooTools Essentials

//This is bad
$$('div.ninja').setStyle('visibility',
'hidden').addClass('invisible');

//It's the equivalent of
$$('div.ninjas').each(function(ninja){
ninja.setStyle('visibility','hidden');
}).each(function(ninja){
ninja.addClass('invisible');
});

//This is better; you only iterate once
$$('div.ninjas').each(function(ninja){
ninja.setStyle('visibility',
'hidden').addClass('invisible');
});
Elements.filter
This method lets you filter the elements based on a selector (unless you
don’t have Selectors.js in your environment, in which case you can
only filter on tag name):
var allDivs = $$('div');
var divsWithClassBlue = allDivs.filter('.blue');
Other Element Methods in Element.js
As I stated previously, MooTools gives a lot of attention to the Element
native. So much so that there are four separate files dedicated to the topic
(outlined next). But Element.js alone contains numerous other methods
that I haven’t covered here—things like toQueryString and
getSelected. These are useful in their own right, but if you understand
the methods that I’ve covered so far, the information in the online
documentation should be easy to follow.

MooTools Essentials
97

Element.Event.js
Any time you want to make a web page interactive, you’re going to have to
deal with events. If the user must click something, you need to tell the
browser that something should happen when they do.
Historically, this was accomplished in a few different ways. There’s the
inline method:
<a href="#" onclick="myFunction()">click me!</a>
The downside to this style of event management is that it’s intrusive. You
must describe the functionality in the same place as the data (the HTML).
With the advent of things like CSS, the whole point is to present the
content generically, and then style it externally. The same principal holds
true for JavaScript.
Another method was to select the element out of the document and describe
the event method as a property of the element:
document.getElementById('foo').onclick = myFunction;
Here the problem is that you can only ever describe one action for each
event. You can’t have more than one onclick, for example.
Then there’s the more modern way of attaching events, which,
unfortunately, is different in Internet Explorer than it is in Firefox or Safari.
Here’s what it looks like in Firefox:
document.getElementById('foo').addEventListener(
'click', myFunction, useCapture
//useCapture = true/false
);
The big problem here is that it’s different in Internet Explorer, so your code
must always have a conditional to do it one way for IE, and another way
for everyone else. Not fun.
98
MooTools Essentials

The other big problem with all three of these options is that they create
potential for memory leaks, especially with closures (see “Closures” in the
Appendix).
Adding and Removing Element Events
MooTools provides us with methods for adding events to elements that
deals with the cross-browser issues and provides a more concise syntax.
Element.addEvent
What it does: Monitors an element for the specified event type (click,
mouseover, etc.), and then executes the specified method, passing that
method the event object that triggered it.
Usage:
myElement.addEvent(eventType, function);
Example:
$('myElement').addEvent('click', function(event){
alert('you clicked me!');
});
When you’ll use it: If you want your users to be able to interact in any way
with the site, you’ll need to attach event listeners to execute your code
when the user does anything.
There are a few important things to note with addEvent:
  The function receives as its argument the instance of the Event class
containing the event object that triggered it (see the Event native
documentation in Chapter 4).
  By default, the object bound to the function (the “this”) is the element to
which the event was attached.

MooTools Essentials
  99

Unlike methods such as Array.each, you cannot specify a third argument to
set a different bound object, so you must use the more explicit
Function.bind to change it if you need to.
Consider these examples:
$('myElement').addEvent('click', function(event){
alert("your mouse is at " + event.page.x +
" by " + event.page.y);
});

//You don't have to declare the event
//argument if you don't use it
$('myElement').addEvent('click', function(){
this.setStyle('border', '1px solid red');
//"this" here is $("myElement") by default
});

$('myElement').addEvent('click', function(){
//Here we bind something else to "this"
//in this case, a slideshow class
this.pageForward();
}.bind(slideShowClass));
Element.addEvents
What it does: Allows you to attach more than one event with a single
method: addEvents.
Usage:
myElement.addEvents(object);
Example:
myElement.addEvents({
click: function(){ alert ('clicked!'); }
});
100
MooTools Essentials

When you’ll use it: If you need to attach more than one event, you can call
Element.addEvent for each one, but you can also use
Element.addEvents to attach several at once. The syntax is basically the
same:
$('myElement').addEvents({
click: function(event){
alert("your mouse is at " + event.page.x +
" by " + event.page.y);
},
mouseover: function(){
this.setStyle('border', '1px solid red');
},
dblclick: function(){
this.pageForward();
}.bind(slideShowClass)
});
Element.RemoveEvent
What it does: Removes an event by passing the function you originally
attached using the same syntax.
Usage:
myElement.removeEvent('click', function);
Example:
var foo = function(){ alert('hi there!'); };
$('myElement').addEvent('click', foo);
$('myElement').removeEvent('click', foo);
When you’ll use it: Sometimes you need to stop monitoring an element for
user interaction. For example, you might only monitor an element until the
user interacts with it once. Other times, you might find that you need to
ensure that there’s only one event listener attached to it. If you have an
event listener that alerts the user to some state when an object is clicked,

MooTools Essentials
101

you might want to remove any other click events on that element before
you add another one.
You can’t, however, remove an anonymous function:
$('myElement').addEvent('click', function(){
alert('hi there!');
});
//This won't work!
$('myElement').removeEvent('click', function(){
alert('hi there!');
});
The reason you can’t do this is because each function here is a different
object. Likewise, you can’t remove a function that you use a method on
when you attach it (like bind or pass):
var say = function(msg){ alert(msg); };
$('myElement').addEvent('click', say.pass('hi there!'));
$('myElement').removeEvent('click', say);
As outlined in “Functions” in Chapter 4, using a method on a function
returns a new function with those values set to it. So say.pass('hi
there!'); is not the same as say. It’s a copy of say with the argument
set.
To work around this, you must keep a reference to the copy:
var say = function(msg){ alert(msg); };
var hiThere = say.pass('hi there!');
$('myElement').addEvent('click', hiThere);
$('myElement').removeEvent('click', hiThere);
Element.removeEvents
What it does: Removes all of the events of a given type (e.g., all onclick
events) or all the events (of any type) entirely.
102
MooTools Essentials

Usage:
myElement.removeEvents([type]);
Example:
//Remove all the click events:
$('myElement').removeEvents('click');
//Remove all the events, regardless of type:
$('myElement').removeEvents();
When you’ll use it: Sometimes you might not have the pointer to a method
that was added (see the preceding examples), or you might want to make
sure that the element doesn’t get the same method added twice (for
instance, if you add an event to alert some data, if you added the event
twice, you’d alert it twice). You can remove all the events or all the events
of a given type with removeEvents.
Element.fireEvent
What it does: Allows you to manually fire any events attached to an
element.
Usage:
Element.fireEvent(type);
Example:
Element.fireEvent('click');
When you’ll use it: Consider something like the onsubmit event for a
form. Perhaps you’re going to use Ajax to update some value on the server
when the user submits the form, but maybe you also have some other event
that might submit it, like if the user hits enter, for instance.
You’d need to first capture the enter event and then submit the form.

MooTools Essentials
103

document.body.addEvent('keydown', function(event){
if (event.key == "enter")
$('myForm').fireEvent('submit');
});
This is a crude example, but it should illustrate the concept. Firing an event
like this isn’t something that happens often, but it does occasionally come
in handy.
Element.cloneEvents
What it does: As outlined in “Creating and Cloning Elements” at the
beginning of this chapter, I show how you can clone elements to create
copies for various purposes, but doing so doesn’t also clone the events
attached to the element. You have to do that manually.
Usage:
myElement.cloneEvents(targetElement[, type]);
Example:
var myCopy = myElement.clone();
//Clone the click events:
myCopy.cloneEvents(myElement, 'click');
myCopy.cloneEvents(myElement); //Clone all of the events
104
MooTools Essentials

Chapter 6: Utilities
MooTools contains several scripts dedicated to helping you implement
code into the page you’re using. I’ve already discussed all the native
prototype extensions (on Element, Function, Array, etc.) and in the next
chapter we’ll cover the Class pattern for writing reusable code. In Chapter
8, I’ll start reviewing some of the classes that MooTools comes with (like
Fx, Drag, and Sortables).
But there’s another group of scripts that kind of exist between these two
groups, composed of functions and extensions that make it easier to
integrate the code you write with an actual HTML document. These are the
scripts in the utilities group.
Selectors
In Chapter 5, I cover the function $$, as well as numerous extensions to the
Element prototype that allow you to collect elements from the DOM.
By default, these methods only allow for tag names as their arguments.
When you include Selectors.js, these methods become much more
powerful. This file extends their functionality to allow for any CSS
selector. It doesn’t change the way you’ll use these methods; it only allows
you to be more specific when you wish to select something from the DOM.
Here’s a basic example:
//Without Selectors.js, all you can select
//on are tag names.
//All the divs on the page:
$$('div');
//All the divs and paragraphs
//note: this returns an array with all the divs first,
//then all the paragraphs:
$$('div', 'p');

MooTools Essentials
105

//When you include Selectors.js, you can
//pass in CSS selectors.
//All the divs with the css class 'myClass':
$$('div.myClass')
//All the paragraphs that are inside divs:
$$('div p');
//All the bold tags in paragraphs with
//Class 'foo' in divs with class 'myClass':
$$('div.myClass p.foo b');
This functionality is applied to any of the methods that accept a selector as
their argument. So in addition to $$, the same is true for the following
element methods:
Element.getElement
Element.getAllNext
Element.getElements
Element.getFirst
Element.match
Element.getLast
Element.getPrevious
Element.getParent
Element.getAllPrevious
Element.getParents
Element.getNext
Element.getChildren
Complex CSS3 Expressions
In addition to standard CSS expressions, as in the examples in the previous
section, Selectors.js also allows you to select on element properties
such as name, value, or href using standard CSS3 expressions (see
//All the mail-to links on the page:
$$('a[href^=mailto:]');
106
MooTools Essentials

The following expressions are supported:
=
The property is equal to the value.
^=
The property begins with the value.
$=
The property ends with the value.
!=
The property is not equal to the value.
*=
The property contains the value.
The property is found when the value is split on spaces (so
~=
~=foo matches “blah foo bar” but not “blahfoobar”).
|=
The property is found when the value is split on dashes (so
|=foo matches “blah-foo-bar” but not “blahfoobar”).
Here are a few more examples:
//All the inputs where name equals 'email'
$$('input[name=email]')
//All the images with urls that end in .gif:
$$('img[src$=gif]')
//All the links without target="_blank":
$$('a[target!=_blank]')
Note that these expressions can take double or single quotes when you
want to search for something that has a space or other character:
$$('input[name!="user[username]"]')
$$('img[src$=".gif"]')
Using Structural Expressions
In addition to the attribute expressions in the previous section, MooTools
on their order in the document—every third paragraph, for example. You
can also do searches for all the enabled form elements, or all the empty
ones.

MooTools Essentials
107

Here are the structural selectors that MooTools supports:
:enabled
The element is not disabled.
:disabled
The element is disabled.
:empty
The element has no children.
:contains(text)
The element’s inner HTML contains the value.
:nth-
This returns every child that matches the
child(expression)
expression (see examples that follow).
:even
This returns every other (even) child.
:odd
This returns every other (odd) child.
:first
The element is the first child.
:last
The element is the last child.
:only
The element is the only child of its parent.
Examples:
//All the paragraphs that are the first child
//of their parents:
$$('p:first');
//Every other link inside paragraphs:
$$('p a:even');
//Every 3rd list item in a specific list:
$$('ul#myList li:nth-child(3n)');
//All the links in paragraphs where the link is
//the last child:
$$('p a:last');
See the online documentation for MooTools for more details, as well as the
documentation for CSS3 selectors.
108
MooTools Essentials

DomReady
In the Appendix, which covers core concepts in JavaScript, one of the
topics I discuss is DomReady.
MooTools implements a custom event for DomReady, and you’ll use it on
nearly every page that includes your JavaScript.
The DomReady Custom Event
What it does: Runs any JavaScript that should wait for the document to
load.
Usage:
window.addEvent('domready', function);
Example:
window.addEvent('domready', function(){
$$('div.error').each(function(div){
div.setStyle('border', '1px solid #F00');
});
});
When you’ll use it: As outlined in the Appendix, the native event that was
historically used was the onload event. This event, however, waits until all
the assets on the page (e.g., images) have loaded before it fires. If you have
code that is meant to run as soon as the document is ready, the earliest
moment you could run it is when the HTML is delivered, but not
necessarily after all the images load. MooTools provides a custom event
(determined by various means for different browsers) for this HTML-is-
ready moment.
Any code that you author that references the DOM (either by collecting
elements, injecting new ones, or altering existing ones) should wait for this
DomReady event.

MooTools Essentials
109

JSON
JSON is a lightweight data-interchange format based on the object notation
in JavaScript. It is a text format that is completely language independent
but uses conventions that are familiar to programmers of the C family of
languages. Think of it as XML for JavaScript.
Declaring a native object in JavaScript looks like this (note that you can
use single or double quotes; it doesn’t matter):
{fruits: ['apple', 'pear'], veggies: ['peas', 'beans']}
In JSON, the same data would look like this:
{"fruits":["apple","pear"],"veggies":["peas","beans"]}
They’re the same for all intents and purposes. The important thing is that
the JSON standard is something that the JavaScript parser can understand.
Consequently, using JSON as a method to transmit data between the client
every programming environment to convert XML to JSON and back again.
MooTools and JSON
MooTools contains methods useful for converting objects to and from
JSON. These methods are fairly straightforward.
JSON.encode
What it does: Converts any object or array into a JSON string.
110
MooTools Essentials

Usage:
JSON.encode(myObj);
Example:
JSON.encode({
fruits: ['apple', 'pear'],
veggies: ['peas', 'beans']
});
//Returns
'{"fruits":["apple","pear"],"veggies":["peas","beans"]}'
When you’ll use it: Mostly you’ll use JSON with Ajax to transmit and
receive data from a server. It’s also possible that you’ll use it to store data
elsewhere (like in a cookie), but mostly it’s used to communicate with
other computers.
JSON.decode
What it does: Allows you to take a JSON string and convert it back into a
native JavaScript object. This is the reciprocal method of JSON.encode.
Usage:
JSON.decode(jsonString[, secure]);
Example:
JSON.decode('{"fruits":["apple","pear"],
"veggies":["peas","beans"]}');
When you’ll use it: As with JSON.encode, this method is likely to be used
when you’re communicating with a server. You’ll use it to decode the
response.
Note that, since JSON data is evaluated by the browser, it represents a
security threat. If the JSON you decode turns out to be malicious code, it
will be run. Consequently, you should ensure that the JSON is either
coming from a secure source (e.g., the same domain as the document) or

MooTools Essentials
111

you should use the secure argument to ensure that the string being
evaluated is an object and not a function.
Json.decode("alert('you just got haxored!')", true);
//Returns null
Cookie
Let’s face it, the interface to manage cookies in native JavaScript is a pain,
which is why if you audit the JavaScript of nearly any web site that uses
cookies, you’ll find functions to do it for you.
MooTools, of course, gives us its own helpful methods for managing
cookies.
Cookie.write
What it does: Allows you to write a cookie value to the client specifying
only the options you need.
Usage:
Cookie.write(key, value[, options]);
Example:
//Simple session cookie
Cookie.write('username', 'fred');
Cookie.write('font-preference', 'large', {
//Make this cookie available to the entire site:
path: '/',
//for 30 days:
duration: 30,
//Make it available to subdomains:
domain: 'mysite.com',
//Only readable if the user is accessing via https:
secure: true
});
112
MooTools Essentials

When you’ll use it: You’ll use this method whenever you want to store
stateful information for the user.
Cookie.read
What it does: Returns the value of a cookie from the client (always a
string) or else returns false if no value was found.
Usage:
Cookie.read(name);
Example:
var preference = Cookie.read('font-preference');
When you’ll use it: You’ll use this method whenever you need to retrieve
the value of a cookie.
Cookie.dispose
What it does: Removes a cookie from the client.
Usage:
Cookie.dispose(name);
Example:
Cookie.dispose('username');
When you’ll use it: You’ll use this method whenever you want to
completely remove a cookie from the client.
Swiff
Adding Flash content to a page is not especially difficult, but there are
some cross-browser issues with how one does it. Additionally, interacting
with that Flash element with JavaScript takes a bit of labor, and
consequently MooTools provides methods to manage this for you.

MooTools Essentials
113

Swiff Constructor
What it does: Creates and returns a Flash object with the supplied
parameters.
Usage:
new Swiff(path[, options]);
Example:
var mySwiff = new Swiff('/flash-movie.swf', {
id: 'myBeautifulMovie'
width: 500,
height: 400,
params: {
wmode: 'opaque',
bgcolor: '#ff3300'
},
vars: {
myVariable: myJsVar,
myVariableString: 'hello'
},
container: $('someElement')
});
Note that when creating the instance of Swiff, if you do not specify a
value for the container option, it does not inject the Flash element into
the document. You’ll still need to do that yourself (see “Swiff.replaces,
Swiff.inject”).
When you’ll use it: You’ll use this method whenever you need to embed
Flash into your pages. It eliminates cross-browser issues and simplifies the
interface for creating these elements.
114
MooTools Essentials

Swiff.replaces, Swiff.inject
What they do: Allow you to inject a Flash object into a document.
Usage:
mySwiff.inject(element[, where]);
//See Element.inject for details
mySwiff.replaces(element);
//See Element.replaces for details
Examples:
mySwiff.inject('myElement', 'after');
mySwiff.replaces('myElement');
When you’ll use them: When you use the constructor for Swiff (i.e., new
Swiff), it creates the element but doesn’t inject it into the document unless
you specify a value for the container option. You’ll use these methods to
put them into the page.
Swiff.remote
What it does: Calls an ActionScript method from JavaScript.
Usage:
mySwiff.remote(function);
Example:
var obj = new Swiff('myMovie.swf');
obj.remote('myFlashFunctionToExecute');
When you’ll use it: This method is useful for running methods in your
Flash file when something happens in the browser and you want to send
information to the Flash environment. Note that your Flash file must be
compiled with the ExternalInterface component. (See the Adobe
documentation on ExternalInterface for more information.)

MooTools Essentials
115

Chapter 7: Classes and Inheritance
MooTools includes mechanisms for tapping into JavaScript’s native
inheritance model (See also “Prototypal Inheritance” in the Appendix). The
syntax looks very similar to the kinds of object-oriented models found in
Java and even uses the name “Class” in the context. Still, it’s important to
understand that the model here is still JavaScript’s.
MooTools classes implement functionality into objects that can be
initialized into numerous stateful instances. Each instance is an object with
methods and properties unique to itself but based on the methods and
properties in the class. Creating an instance of, say, Widget and assigning
it specific values (options like location, visibility, etc.) returns that instance.
You can then create another instance of Widget with different options and
execute methods on either of them without affecting the other.
In my experience, there are two types of code in JavaScript: reusable code
and implementation code. The former includes all the things that you might
ever want to use again—date pickers, form validators, sortable tables,
whatever. The latter is the code you write on a specific page to tell it that
these things are present and configured for the current content. All your
implementation code should be a set of namespaced functions
(myPage.load, myPage.search, etc.), and everything else—the reusable
code—should be classes (FormValidator, DatePicker, Gallery). In this
way, every page sets up new instances of these classes, passing along the
data and configurations for them that are unique to the given environment.
Using the Class Constructor
What it does: The Class constructor creates functionality for defining
reusable Class objects that can be extended and inherited from.

MooTools Essentials
117

Usage:
new Class(properties);
Example:
var SimpleClass = new Class({
initialize: function(options){
this.options = options;
},
someProperty: 'foo',
someMethod: function(msg){ alert(msg); }
});
When you’ll use it: MooTools contains a very elegant structure for
authoring functionality that can be extended and altered in different
contexts. JavaScript itself has the core capacity for this functionality, but
no native methods to make use of it. Historically, people either didn’t make
use of it or had to author their own methods to be able to make use of the
inheritance model in JavaScript.
Making best use of JavaScript’s prototypal inheritance model requires that
you understand that model well. It’s important that you grasp how
JavaScript’s constructor model works (see “‘this’ and Binding” in the
Appendix) and how JavaScript’s prototypal inheritance model works (see
“Prototypal Inheritance” also in the Appendix).
Binding and prototypal inheritance are the two concepts at the heart of
MooTools, and very little functionality in the library avoids using them.
The core functionality for managing inheritance is the Class function.
Remember that by convention, any function that begins with an uppercase
letter requires the use of the new constructor when using it. So every class
that you author should begin with an uppercase letter so that you know it
needs new to initialize it.
118
MooTools Essentials

The properties argument is an object of name/value properties for the
class that defines what each instance should have when it is initialized. Say
you have the following very simple class:
var Human = new Class({
isAlive: true,
energy: 1,
eat: function(){
this.energy++;
}
});
You’ve now defined some very simple functionality for your Human class.
Whenever you want a new instance of Human, you just call it with the new
constructor:
var bob = new Human();
This instance—bob—is an instance of Human, and it has the properties
isAlive, energy, and eat. These properties have the default values
defined in your Human class, but you can change them easily enough.
bob.eat(); //bob.energy is now 2
Initialization
When classes are invoked with their constructor, all the properties in the
object passed in are applied to the new class and are available to each
instance (like with Human.eat earlier). MooTools looks for a special
property called initialize that it will execute whenever a new instance is
created.

MooTools Essentials
119

Here’s what that might look like:
var Human = new Class({
initialize: function(name, age){
this.name = name;
this.age = age;
},
isAlive: true,
energy: 1,
eat: function(){
this.energy++;
}
});
var bob = new Human('Bob', 20);
//bob.age = 20
//bob.name = 'Bob'
Here you have a class with default properties and methods (like isAlive
and eat), but not all Humans are necessarily the same, so you allow
arguments to be passed to the constructor, which are passed to the
initialize method at invocation.
Classes aren’t required to have an initialize method. If you have a class
that doesn’t do anything when you initialize it, you can omit this method.
Classes that are meant to be implemented by other classes (see
“Implementing Classes into Other Classes” later in this chapter) usually
don’t have an initialize method because they would overwrite the
method in the class that you blend them into. Otherwise, you’ll use this
method to set up the state of the class when the user creates it. Often
options and arguments are passed in, and the initialize method stores
those in the instance of the class and maybe processes them.
Inheritance
Creating classes is a really powerful way to reuse functionality. You can
define all the methods and default values for a widget or UI component and
120
MooTools Essentials

then create new instances of those things over and over again. If you
discover a bug in your code, you only have to fix it in one place. It’s
object-oriented programming in JavaScript, which for a long time was a
concept that just didn’t seem to be in the language.
But even this basic ability is somewhat limited if you can’t extend that
functionality when you need to. If you have a class that validates form
inputs, that’s awesome, but what if you need to make a class that does so a
little differently? Copying all that code into another class doesn’t make
sense, and thankfully you don’t have to.
MooTools offers two ways to get more out of the classes that you write
with Extends and Implements—two special properties of classes that let
you get more mileage out of the code you write.
Implement vs. Extend
The Extends property is used to employ another class as a blueprint for the
one you are creating, while the Implements property is used to enumerate
other classes whose methods should be added to the one you are creating.
In addition to these two properties are two methods for extending and
implementing classes: Class.extend and Class.implement.
Class.extend is used to add properties directly to a class, while
Class.implement modifies the prototype of the class.
These distinctions are further explained next, as it’s important that you
learn when to use each if you want to get the full power of MooTools.
Extending Classes
Classes have a special property called Extends that allows you to build
upon another class very easily. As stated earlier, Extends specifies an
object (a Class) that will act as the template for the new class you define.
Let’s build on the Human class shown earlier and make a Ninja class.

MooTools Essentials
121

for energy as 1, but ninjas get 100. This will override the value for energy
defined in Human.
Then there’s the initialize method. Both classes have one, and here you
see a special property for methods: this.parent. Classes that extend
other classes can have overlapping methods but retain the ability to execute
the method that they overwrite. In this way, you can extend a method in a
class, with logic executed before and/or after the parent method is called.
Extends is quite powerful, allowing you to overwrite methods in the
parent class and optionally execute that overwritten method. Note that you
must still pass the arguments to the parent method that it expects to receive,
even if the new method you’ve defined takes different arguments. By using
Extends, you can create small classes that do one thing well and then build
upon them with more specific functionality. The result is more reusable
code.
Extending Classes into Themselves
Extending a class into itself allows you to alter the way its instances behave
without creating a new name for the result. You essentially get to add more
stuff to the class itself. Why do this? Say you want to alter a class in a
particular environment without changing it everywhere.
Here’s an example of what this would look like:
//Continuing from the Human and Ninja classes earlier
Ninja = new Class({
Extends: Ninja,
kills: 0,
attack: function(target){
this.parent(target);
this.kills++;
}
});

MooTools Essentials
123

Here you add functionality to the Ninja class—now you can keep track of
how many targets each Ninja has offed (I know, it’s a bit morbid, but hey,
that’s just how ninjas are—it’s what they do). But you can see the
advantage; you can still call the parent method as defined in what used to
be Ninja.attack, so you don’t have to rewrite that logic. You can add
your own additional logic that happens before or after you call the parent
function.
The only downside to this method is that any instances of Ninja that have
already been created (as well as any classes that have already been created
by extending this one) will not have this functionality, so it’s important that
you have this kind of extension defined before you create any instances of
the class or extend it further.
Implementing Classes
Extending classes allows you to create new classes based on the templates
of old ones, making use of the properties defined in the parent classes,
adding new properties, and overwriting ones that you wish to alter. But
what if you want to change how an existing class works? That’s where
implementing classes comes into play.
Implementing functionality into classes has one big positive and one big
negative. On the positive side, when you implement functionality into a
class, all instances of the class are affected immediately (unlike using
Extends to extend a class back onto itself, as discussed in the preceding
section). On the negative side, you don’t have access to what used to be
defined for methods—there’s no this.parent. You must overwrite the
entire property when you implement changes. This is because implement
changes the prototype of the object you are modifying, essentially altering
the parent instead of the object itself.
124
MooTools Essentials

There are two ways to implement functionality into a Class. The first is to
use a method that comes with every class called implement. Here’s what it
looks like:
//Continuing from our Human and Ninja classes earlier
Ninja.implement({
kills: 0,
attack: function(target){
target.isAlive = false;
this.energy = this.energy - 5;
this.kills++;
}
});
Unlike with the example in the “Extending Classes into Themselves”
section, you can’t reference this.parent, so you must reauthor all of the
functionality in the attack method. This can be a real pain, which is why
extending classes into themselves is so useful.
Implements is really meant to be used to combine classes, and
consequently there is no notion of a parent. If you add all the methods of
class A into class B, class B now has the methods of class A in its
prototype, but there is no “parent” relationship between class A and class
B, which brings us to the next section.
Implementing Classes into Other Classes
It’s much more likely that you’ll use implementing to add functionality
from one class to another via the Implements property. By implementing
functionality from class into another, you can identify patterns that are
shared across numerous classes and push that functionality into all of them.
This creates an enormous opportunity to not only deliver less code to the
browser, but also reuse what you write.
Consider this example:

MooTools Essentials
125

difference here is that the Warrior methods and properties don’t overlap
with anything in the Human class.
Implements is mostly used with helper classes—collections of commonly
used functionality that often gets employed in numerous classes. Examples
of these include the Options class and the Events class.
The idea here is to project small bits of reusable functionality into your
classes. If you write things well, you end up with all these little LEGO-like
blocks that can be snapped together to get robust functionality, while each
individual class does one thing specifically.
The best way to understand the potential of MooTools’ class architecture is
to look inside MooTools itself. The library is comprised of lots of these
little blocks, and it extends and grows on itself to provide robust
functionality, while each piece is as simple as it can be.

MooTools Essentials
127

Chapter 8: Getting Started with Classes
Chapter 7 covers the basics of writing classes. These reusable chunks of
code are the building blocks of your application. MooTools itself offers
numerous classes for you to use to create effects, drag functionality,
tooltips, and more.
In this chapter, I’ll cover some of the basics of using these classes. The
conventions outlined here are true of nearly all the classes that come with
MooTools and will likely be true of most of the classes you write for your
own use.
Class.Extras
Because two of the goals of MooTools is to make it easy to reuse code and
to eliminate duplication of effort, several patterns get used over and over
again in MooTools.
Three commonly used patterns in MooTools classes are options, events,
and chaining. Class.Extras.js contains three classes that are designed to
be implemented into other classes; they aren’t very useful on their own, but
implemented into another class, they make that class much more useful.
The Options Class
What it does: This class is designed to be implemented into other classes.
The options convention allows users to pass in none, some, or all of the
optional values for a class, overwriting only the default values that they
need to. By defining default behaviors in your class, you can make the
interface both highly flexible and easier to use.
When you look at the documentation for a MooTools class, you’ll see these
defined as a list of named arguments that can be passed in (or not) along
with their default values.

MooTools Essentials
129

These options passed in are then passed to the setOptions method defined
in the Options class. Because you are implementing the Options class
into your class, this method is now part of your class, too.
Usage:
new Class({
Implements: Options,
options: { /*default options*/ },
initialize: function(arg1, arg2, arg3, options){
this.setOptions(options);
}
});
Example:
var Widget = new Class({
Implements: Options,
options: {
color: '#fff',
size: {
width: 100,
height: 100
}
},
initialize: function(options){
this.setOptions(options);
}
});
var myWidget = new Widget({
color: '#f00',
size: {
width: 200
}
});

//myWidget.options is now:
//{color: #f00, size: {width: 200, height: 100}}
130
MooTools Essentials

When you’ll use it: The options convention blends together the default
values (using $merge). This allows you to define a default state for your
class that users can easily override, but doesn’t force them to specify all the
possible values. The result is a very flexible class with as many options as
you care to implement without overloading the interface to the class. It also
has two other nice consequences: 1) you don’t end up with classes that
require a dozen arguments, and 2) if you change the options in the class at a
later date, you don’t have to go find all the places that reference the class to
create a compatibility layer to accomodate old code that still uses the old
options.
Note
In general, you should consider the options object read-only in
your code. You can (and should) reference this.options in your code to
read the state that the user has defined, but you should not alter it directly.
Instead you should use setOptions to alter it.
...
this.setStyle('color', this.options.color); //Yes
this.options.color = '#000000'; //No
this.setOptions({color: '#000000'}); //Yes

The Events Class
Another often-used pattern for classes are events. These work just like the
events on elements (like onclick), and the interface is the same. Using
Events in your classes allows flexibility where the class might do
something in response to some other action. The events you define provide
hooks into these actions. Consider a slideshow, for example. You might
have events for when the user clicks forward or backward and events for
when the user reaches the end of the slideshow (or back up to the start).

MooTools Essentials
131

Because your class handles all these behaviors, the appropriate place to put
the logic to determine that these actions occur are in your class. Later,
when you implement an instance of the class into your page, you might
need to add additional functionality that should run when these events
occur.
addEvent, addEvents, fireEvent, removeEvent, removeEvents
What they do: These methods work much like their countparts on the
Element prototype, allowing you to attach functions to specific events.
Usage:
new Class({
Implements: Events,
complete: function(){
this.fireEvent('complete');
}
});
Example:
var Widget = new Class({
Implements: Events,
initialize: function(element){
...
},
complete: function(){
this.fireEvent('complete'[, arguments]);
}
});

var myWidget = new Widget();
myWidget.addEvent('complete', myFunction);
When you’ll use them: Unlike Element, there is no concept of a “native”
event (like onclick or onmouseover) for a class. The events on a class are
whatever you choose to call them. In order for them to be useful, you must
include in your class calls to fireEvent for them to be executed. By
132
MooTools Essentials

adding events to your class, you make it much more useful in different
contexts.
Note
By convention, events on classes always begin with “on”—
onComplete,  onFailure, and so forth—in the options. However, you can
attach methods to events without the “on,” so onComplete just becomes
complete when you attach a method to the event (e.g.,
myFx.addEvent('complete', myFunction)).  More  on  this  in  the  next
section.
Events and Options
When you implement both Options and Events into your class, a bit of
special magic occurs. When users initialize the class and pass in options,
they can pass in event options as well. These will automatically get passed
to addEvent when you pass the options to setOptions.
Example:
var Widget = new Class({
Implements: [Events, Options],
initialize: function(element, options){
this.element = $(element);
this.setOptions(options);
},
complete: function(){
this.fireEvent('complete', this.element);
}
});
var myWidget = new Widget($('myElement'), {
onComplete: myFunction
});
Here the user has passed in as one of the options a function for
onComplete. When you pass the options to setOptions, any option that

MooTools Essentials
  133

begins with “on” that is a function will be passed to addEvent
automatically for the complete event.
Note
Any options that begin with “on” that are functions will be
removed from the options when you pass the options to setOptions. This
means that if the user passes in a function for onComplete, in the options,
this.options.onComplete won’t be defined, as it’s removed in the
process.
Note
You can actually reference either the event with “on” or without
it. If you use fireEvent or addEvent and reference onComplete or
complete, you’ll get the same result. By convention, MooTools drops the
“on” for both element events and class events for consistency, but if you
use the “on” with classes, it’s smart enough to know which one you’re
referring to.
The Chain Class
MooTools also contains functionality similar to Events that lets you build
a chain of functions to execute one after the other. Think of this as “when
you’re finished, do this next thing” functionality.
Chain.chain
What it does: The chain method pushes a function onto a stack of
methods defining the order of things to do next. When the method is
executed, it is removed from the stack.
Usage:
var Widget = new Class({ Implements: Chain });
Widget.chain(function);
134
MooTools Essentials

Example:
var Widget = new Class({
Implements: Chain,
someMethod: function(){
//Some code that does stuff
this.callChain();
}
});
Widget.chain(function(){ alert('this comes next!'); });
Widget.someMethod();
//Alerts the message when someMethod finishes
When you’ll use it: This method gets used mostly in the Fx class.
Typically, it’s used when a class does something immediately and then
completes, and often the class also has an onComplete event that is fired at
the same time.
The difference between adding a method to a chain and adding it as an
event is that when you add it as an event, it will get fired every time the
event is fired (until you remove it), while a chained function will only get
called once. Here’s an example of it working on its own (which isn’t that
useful):
var myChain = new Chain();
myChain.chain(
function(){ alert('do dishes'); },
function(){ alert('put away clean dishes'); }
);
myChain.callChain(); //Will alert 'do dishes'.
myChain.callChain(); //Will alert 'put away clean
// dishes'.

MooTools Essentials
135

And here’s a more useful example using Fx.Tween:
var myTween = new Fx.Tween(myElement);
myTween.start('opacity', 0).chain(function(){
myTween.start('opacity', 1);
});
Chain.callChain
What it does: This calls the next method on the chain stack, passing any
arguments passed to it (they are optional).
Usage:
myChain.callChain(arguments);
Example:
See the example in “Chain.chain” earlier.
When you’ll use it: In order for the Chain class to really work, you have
to call the next method on the stack whenever the operation that’s being
performed is complete. Consider an effect—let’s say you’re fading the
element in using its CSS opacity property. Over the duration of the effect,
you repeatedly increment the value of the opacity until it reaches 1, and
then you stop. At this point, you must execute this.callChain to call the
next method on the chain stack.
Chain.clearChain
What it does: This removes all methods from the chain stack.
Usage:
myWidget.clearChain();
When you’ll use it: Sometimes it’s necessary to clear the chain to stop a
behavior from continuing. This is especially true if you add things to the
chain from within the class itself (which in general I don’t recommend).
136
MooTools Essentials

Chapter 9: Fx
Now comes the fun part of MooTools—the effects. Everything I’ve
covered up to this point has been about the utility of writing JavaScript
with MooTools and how to do so efficiently and without duplicating code.
But the effects are where MooTools really shines.
Fx and Fx.CSS
The Fx class is one you’ll likely not use directly. It’s a foundation layer for
all the other effect extensions. You’re more likely to use the extensions
than you are these two core files, so I’m not going to spend a lot of time on
them. It’s conceivable that you might extend one or the other to write your
own effect, but even that is doubtful; if you were to undertake writing an
effect, it’s more likely you’d extend Fx.Tween, Fx.Morph, or
Fx.Elements (which MooTools considers a plug-in).
What is interesting and useful to learn about the Fx class are the options
and methods it defines, as all the other effects extend these and add to
them.
Fx Options
Every effect extension accepts the following options in addition to any
arguments and options that are defined by the extension. This is straight
from the MooTools documentation:
  fps: (Number: defaults to 50) The frames per second for the transition.
  unit: (String: defaults to false) The unit, for example, “px”, “em”, or “%”.
See Element.setStyle in Chapter 5.
  link: (String: defaults to “ignore”) Can be “ignore”, “cancel”, or “link”.
  “ignore”: Any calls made to start while the effect is running will be
ignored.

MooTools Essentials
  137

  “cancel”: Any calls made to start while the effect is running will take
precedence over the currently running transition. The new transition will
start immediately, canceling the one that is currently running.
  “chain”: Any calls made to start while the effect is running will be
chained up and will take place as soon as the current effect has finished,
one after another.
  duration: (Number: defaults to 500) The duration of the effect in
milliseconds. Can also be one of the following:
  “short”: 250 ms
  “normal”: 500 ms
  “long”: 1000 ms
  transition: (Function: defaults to Fx.Transitions.Sine.
easeInOut) The equation to use for the effect; see “Fx.Transitions” later in
this chapter. Also accepts a string in the following form:
  transition[:in][:out]: For example, “linear”, “quad:in”, “back:in”,
“bounce:out”, “elastic:out”, “sine:in:out”.
Fx Events
Much like the preceding options, all effect extensions have these events
(though they may have more):
  onStart: The function to execute when the effect begins.
  onCancel: The function to execute when you manually stop the effect.
  onComplete: The function to execute after the effect has processed.
  onChainComplete: The function to execute when using link 'chain'
(see options earlier). It gets called after all effects in the chain have
completed.
138
MooTools Essentials

Fx.start
What it does: All the effect extensions have a start method that starts the
effect, which will continue until the transition is complete or the effect is
canceled.
Because each extension changes different things (Fx.Tween changes a
single style property, Fx.Morph will change many, and Fx.Elements will
change numerous style properties across numerous elements), the argument
passed to start differs from extension to extension.
When start is called, it fires the onStart event and begins the transition.
If only one parameter of a transition is defined, the CSS property will be
transitioned from its current state to the one defined.
Usage:
myEffect.start(arguments);
Example:
new Fx.Tween($('myElement')).start('opacity', 1);
When you’ll use it: This method will transition the opacity of the element
from its current state (if no starting state is specified) to the state specified.
If the element is already at that state, no transition will occur (though the
onComplete event will still be called and the chain will still be called—
see “The Chain Class” in Chapter 8).
Here we specify the starting state:
new Fx.Tween($('myElement')).start('opacity', 0, 1);
This will transition the opacity from zero to one, regardless of the current
state.

MooTools Essentials
139

Fx.set
What it does: The set method works just like the start method, except
no transition is applied (and neither the onComplete method nor the chain
is called).
Usage:
myEffect.set(arguments);
Example:
new Fx.Tween($('myElement')).set('opacity', 1);
//Opacity is immediately set to 1
When you’ll use it: The set method is useful to quickly reset the state of a
CSS property. For Fx.Tween, it’s not much different from
Element.setStyle, but for something like Fx.Scroll or Fx.Elements,
set is a bit more useful in allowing you to change the state of the effect.
Fx.cancel, Fx.pause, Fx.resume
What they do: These methods let you stop an effect entirely (Fx.cancel)
or pause it and resume it later (Fx.pause, Fx.resume). Fx.cancel will
fire the onCancel event (but does not call the chain method; instead it
clears the chain with clearChain).
Usage:
myEffect.pause(); //Pauses the effect
myEffect.resume(); //Resumes a paused effect
myEffect.cancel(); //Cancels a running effect entirely
When you’ll use them: It’s actually somewhat rare that I find myself using
these methods, but there are occasions where user interaction might cause
you to pause or cancel an effect. Note that when you pause or cancel an
effect, the CSS property that was being transitioned will be left in whatever
state it was in when you stopped the effect. So if you’re fading something
140
MooTools Essentials

in and then stop the transition halfway through, the element will still be in
that halfway state. You can use Fx.set in a case like this to set the state to
whatever you want.
Fx.Tween
What it does: The simplest effect you’ll likely use is Fx.Tween. This class
transitions a single CSS property from one state to another. It’s deceptively
easy to use. When used properly, you can use it to create a highly engaging
and expressive user experience.
Usage:
new Fx.Tween(element[, options]);
Example:
var myEffect = new Fx.Tween($('myElement'), {
property: 'width',
duration: 500, //Transition over half a second
});
//Transition from 0px wide to 100px wide:
myEffect.start(0, 100);
//Transition from the current width to 200px:
myEffect.start(200);
//You can also specify the property in the
//start method instead of the options
var myEffect = new Fx.Tween($('myElement'));
//Transition opacity to 1:
myEffect.start('opacity', 1);
//Transition width from zero to 100:
myEffect.start('width', 0, 100);
When you’ll use it: Fx.Tween is the most basic effect in MooTools. When
you need to fade something in or move it to a new location or change its
size or color, Fx.Tween is all you need.

MooTools Essentials
141

Element.tween
What it does: Many of the effects extensions also extend the Element
prototype to provide shortcuts to start an effect.
Usage:
myElement.tween(property, startvalue[, endvalue]);
//If endvalue isn’t set, startvalue will be used for
//the end value, and the start value will be the
//current value
Example:
//Transition opacity to 1:
$('myElement').tween('opacity', 1);
//Transition width from 0 to 100:
$('myElement').tween('width', 0, 100);
When you’ll use it: This shortcut method not only saves you a few
keystrokes, but also makes your code a little easier to read. I use it almost
all the time that I want to tween an element, so maybe the title here should
be “When you won’t use it.” The reason not to use it is when you need to
have more than one effect to use for different properties. Maybe you have
one transition that you use for showing an element (with different
transitions, durations, etc.) than the one for hiding it. You could change
these values before using the shortcut again, or you could have two
instances of the effect.
Using Element.get/set with Fx.tween
What they do: The shortcut is managed using element storage (see
Chapter 5). When you first use the shortcut, a new instance of Fx.Tween is
created and stored for the element as “tween.” Subsequent calls to this
shortcut just reuse this instance. This means you can modify the properties
of this “built-in” version of Fx.Tween by using Element.get and
Element.set (see Chapter 5).
142
MooTools Essentials

Usage:
//Set the options for the "built-in"
//instance of Fx.Tween:
myElement.set('tween', options);
//Retrieve the "built-in" instance of Fx.Tween:
myElement.get('tween');
Examples:
//Cancels a running effect:
myElement.get('tween').cancel();
myElement.set('tween', {
//Change the duration for the "built-in" instance:
duration: 1000
});
When you’ll use them: These two methods are useful in managing the
instance of Fx.Tween that gets created when you use the .tween shortcut.
Setting the options for the duration or transition, for example, gives you
greater control over what the effect looks like. Just be aware that there’s
only one of these built-in instances. If you need more than one instance,
you’ll need to use the constructor (new Fx.Tween).
Fx.Morph
What it does: This class is very similar to Fx.Tween in most respects
except that it allows you to transition more than one property at the same
time.
Usage:
var myEffect = new Fx.Morph(element[, options]);
myEffect.start(to);

MooTools Essentials
143

Example:
var myEffect = new Fx.Morph($('myElement'), {
duration: 1000
});
myEffect.start({
width: 100, //Transition the width to 100
height: [0, 100], //Transition height from 0 to 100
opacity: 1 //Transition opacity to 1
});
When you’ll use it: You can use Fx.Morph to achieve the same results as
Fx.Tween (specifying only one property to transition), but really this class
is useful when you’re transitioning several attributes at once.
Element.morph
What it does: Just like Element.tween, Element.morph is a shortcut to a
“built-in” instance of Fx.Morph.
Usage:
myElement.morph(to);
Example:
$('myElement').morph({ width: 100, height: 100});
When you’ll use it: As outlined with Element.tween, this shortcut to the
“built-in” instance of Fx.Morph is what I use most of the time. The times
when you won’t use it are the same with Fx.Tween/Element.tween, so
I’ll direct you to the earlier section where I go into those details.
Element.set/get with Fx.Morph
You can use Element.set and Element.get to access the “built-in”
instance of Fx.Morph just as with Fx.Tween. I won’t illustrate that here,
but read the earlier section on how its done with Fx.Tween and refer to the
MooTools documentation for more.
144
MooTools Essentials

Using CSS Selectors with Fx.Morph
What it does: One of Fx.Morph’s neat tricks is the ability for you to pass it
a CSS selector instead of an object with properties to change. Think of this
as analogous to Element.addClass, where you add a CSS class and this
changes the style of the element, except here it does so with a transition
(note that only numerical properties and colors are changed—changes to
font family or background image would occur instantly).
Usage:
myElement.morph(selector);
Example:
$('myElement').morph('.myCssClass');
When you’ll use it: One of the problems with using effects to transition
style properties is that you end up incorporating aspects of your design into
the code that defines interaction. We have clear lines between presentation
(CSS) and data (HTML), and between data (HTML) and interaction
(JavaScript), but the lines between interaction (JavaScript) and design
(CSS) are somewhat blurry. We use JavaScript to change the layout, and in
the process we add all these CSS instructions to our code.
To a certain extent, this is unavoidable. But Fx.Morph’s ability to accept a
CSS selector allows us to remove at least some of the CSS properties from
the layout.

MooTools Essentials
145

Note
Using this functionality does not actually add the class to the
element being transitioned. If you want the result of a morph operation to
end with the element having the class applied, use the chain method:
myElement.morph('.myCssClass').chain(function(){
myElement.addClass('myCssClass');
});

Fx.Transitions
By default, all the effects classes use a sinodal equation for their
transitions, but if you include Fx.Transitions.js, you get several other
ones that can create more expressive interactions.
The Transitions
Briefly, here are the transitions you get when you include this script:

146
MooTools Essentials

MooTools Essentials
147

148
MooTools Essentials

MooTools Essentials
149

Specifying a Transition for an Effect
When you initialize an effect, you can use the default transition
(Liniear.easeInOut) or you can specify any of the transitions shown in
the preceding section.
Example:
var effect = new Fx.Tween(myElement, {
transition: Fx.Transitions.Elastic.easeInOut
});
Because this is a lot of typing to do, MooTools provides shortcuts to each
of the transitions. Here’s the same thing as the preceding example, only this
time using the shorthand for the transition:
var effect = new Fx.Tween(myElement, {
transition: 'elastic:in:out'
});
Creating Your Own Transition
If you are a hard-core math whiz, you can actually create your own
transitions. I’m not going to go into how to do this here, but I wanted to
mention it. If you’re interested, look at the MooTools documentation on the
Fx.Transition class and then look at the source of Fx.Transitions.js.
150
MooTools Essentials

The Rest of Fx.*
MooTools file organization gets rearranged periodically as our thinking on
how best to organize the codebase changes and shifts. The classes and
methods don’t change much (and where they do a compatibility layer is
provided), but the location of these things often do.
Currently, the Fx group consists solely of Fx, Fx.CSS, Fx.Tween,
Fx.Morph, and Fx.Transitions, but these aren’t the only effects classes
that MooTools has to offer.
The rest are in the plug-ins group. I discuss these in greater detail in
Chapter 11, but, briefly, they could be described as classes that are not
fundmentally required to build a good web experience with MooTools.
Classes like Drag or Tips are things that most web experiences can do
without.
The same can be said of the other effects libraries:
  Fx.Slide: This effect slides elements in and out of view (I think of this
effect like an old timey cash register that slides up the values of what you
owe).
  Fx.Scroll: This effect is used to smoothly scroll any overflown element
(including the window).
  Fx.Elements: This effect is used to transition numerous styles on numerous
elements.
You’ll see more on these in Chapter 11.

MooTools Essentials
  151

Chapter 10: Request
If there’s any technology most associated with Web 2.0, it’s Ajax. Short for
Asynchronous JavaScript and XML, Ajax refers to the process of sending
and receiving data to and from a server without reloading an entire page.
The native tools for doing this are tied up in a JavaScript object called
XMLHttpRequest. Microsoft actually introduced the technology for
support for Outlook Web Access 2000. In IE, it showed up as an ActiveX
object called XMLHTTP. Since then it’s been implemented as a native
JavaScript object (called XMLHttpRequest) for every browser except
Internet Explorer, which still uses the ActiveX control.
The obvious problem with these native solutions is that you have to use
different objects for different browsers, but even if you look at the standard
XMLHttpRequest object, the interface leaves a lot to be desired.
This is where MooTools comes to our rescue, providing us with three
classes that make Ajax much more pleasant to work with: Request,
Request.HTML, and Request.JSON.
Request
What it does: The Request class is for standard request/response
interactions when you need to send and/or receive data to and from the
server.
Usage:
new Request(options);

MooTools Essentials
153

Example:
var myRequest = new Request({
url: '/requestHandler.php',
method: 'get',
onSuccess: function(responseText, responseXML) {
alert(responseText);
}
});
myRequest.send('username=johndoe&first=john&last=doe');
//OR
myRequest.send({
username: "johndoe",
first: "john",
last: "doe"
});
When you’ll use it: Making an interactive web experience will almost
always include sending information about state changes to a server and
requesting new information on demand. If a user can drag and drop and
reorder items in a list, you’ll need to send the new order to the server for
storage. If the user clicks a discussion thread to expand it and see the
contents of that thread, you need to fetch that content to display it if you
don’t deliver it when the page loads. These kinds of interactions are
increasingly part of the user’s expectations.
For example, consider something as simple as rating a product on a scale of
one through five stars. Users expect to be able to click the star of their
choice and see that decision immediately reflected. If the page reloaded
entirely, they would feel that something was off. As users continue to
expect more and more interactive experiences, our use of Ajax will grow.
154
MooTools Essentials

Note
Request has several events that you can use in your code:
  onSuccess: This event is fired whenever the instance receives a
successful response from the server. It is passed two arguments:
responseText and responseXML.
  onFailure: This event is fired whenever the instance receives an
unsuccessful response from the server (like 404). It is passed as its
argument the instance of the request object (either XMLHttpResponse
or the XMLHTTP ActiveXObject in the case of Internet Explorer).
  onCancel: This event is fired whenever a running request is canceled. It
is not passed any arguments.
  onException: This event is fired whenever there is an exception when
setting the headers of the XMLHttpResponse object.
  onRequest: This event is fired whenever the instance actually sends a
request. It is not passed any arguments.
  onComplete: This event is fired whenever onSuccess or onFailure
occur. It is passed the same arguments as onSuccess or onFailure.

Request Options
The Request class has numerous options fully outlined in the MooTools
documentation. You can see a few of them illustrated in the preceding
example, but it’s important that you spend some time looking at the current
documentation to learn about the various ways you can configure the class.
Request.send

MooTools Essentials
  155

What it does: When you create an instance of Request, no data is sent
until you invoke its send method, which sends the request to the server.
Usage:
myRequest.send();
myRequest.send(object);
myRequest.send(queryString);
Example:
var myRequest = new Request({
url: '/requestHandler.php',
method: 'get',
data: {
layout: 'compact'
}
});
//Send the default data, layout=compact:
myRequest.send();
//Overwrite the data default:
myRequest.send({layout: 'extended'});
When you’ll use it: This method accepts as an optional argument the data
to include in the request. There is also a data option when you instantiate
the class where you can specify default information. This gives you the
ability to reuse an instance of Request repeatedly, sending different
information with each request.
Why would you want to reuse the class? Well, for instance, you can set the
link option to “cancel” so that you can let the user initiate numerous
requests but only use the last one. Consider an interface where users can
filter data by checking check boxes. Each time they click your code
requests new, filtered information from the server. By reusing the request
and canceling previous requests, you can fetch only the most recent state
that the user has created.
156
MooTools Essentials

Note
For security reasons, you can request data only from the same
domain as the page (this restriction applies even to subdomains, so you
discussion on my JsonP class in Chapter 12), but not with Ajax, and they
should be used sparingly.
Request: .get, .post, .put, .delete
The Request class offers shortcut methods that work just like
Request.send except that they use different “method” arguments in the
request. Also, these shortcuts can accept an optional first argument for the
URL.
Examples:
//Send the request as a "get":
myRequest.get({username: 'johndoe'});
//Send the request as a "post":
myRequest.post({username: 'johndoe'});
//Send the request as a "put":
myRequest.put({username: 'johndoe'});
//Send the request as a "delete":
myRequest.delete({username: 'johndoe'});
//Each of these can take a url, too:
myRequest.delete('/delete_user', {username: 'johndoe'});
Request.cancel
What it does: This method simply cancels a running request.
Usage:
myRequest.cancel();

MooTools Essentials
157

When you’ll use it: As illustrated in the earlier section “Request.send,”
there are times when you need to stop listening for a response and instead
send a new state to the server. By canceling the request, you’ll prevent the
onSuccess, onFailure, and onComplete events from firing. So, for
example, if you have an effect that displays a message that a user’s changes
have been set to occur onSuccess, and the user makes a change followed
by another quick change before the first one has received a response, you
can cancel the first request and send a new instruction. Your message will
only display when the second one returns.
Note
This does NOT cancel the request to the server. Rather, it
instructs the client (the browser) to stop listening for a response. So, for
example, if a user clicks “delete” on an item, and you send a request to the
server to remove something from that user’s account, you can stop
listening for the server to respond to this request, but the server has
already been sent the instruction.
Element.send
What it does: MooTools integrates a shortcut into the Element prototype
to make it easy to send information based on the contents of any DOM
element that contains input elements (typically a form).
Usage:
$('myForm').send(url);
158
MooTools Essentials

Example:
$('myForm').set('send', {
onSuccess: function(response){
alert(response);
}
}).addEvent('submit', function(event){
event.preventDefault();
this.send(); //Uses the URL from “action”
});
When you’ll use it: Like all the Element methods that allow you to invoke
a class (as with the effects shortcuts), this just saves you keystrokes. When
you use this method on a form, the parameters of the form (the method and
the URL) and all the input values are used just as if the form had been
submitted. The only difference is that the data is sent with Ajax.
Using Element.set with Element.send
As with the other shortcuts (as discussed previously in Chapter 9), you can
get at the “built-in” instance of Request using Element.get and
Element.set. This will allow you to set the default state for that instance.
Example:
//Set a default value for this element's
//Request instance:
myElement.set('send', {method: 'post'});
//Retrieve this element's Request instance
//and cancel it:
myElement.get('send').cancel();
Request.HTML
What it does: This extension to the Request class automates updating the
content of a DOM element with the response of an Ajax request.

MooTools Essentials
159

Usage:
new Request.HTML(options);
Example:
new Request.HTML({
url: '/userprofile.php',
data: {
userid: '1001'
},
update: $('userProfileDiv');
}).send();
When you’ll use it: A very common pattern implied by the Web 2.0
buzzword is the use of Ajax to fetch display data from the server on
demand. If a user expands a section of content, rather than have that
content loaded and hidden, it’s fashionable to instead go get the layout that
belongs there only if and when the user requests it.
There are some trade-offs to this practice. It means that this content is not
visible to search engines, for example. But for the most part I encourage
this practice. When used well, it can increase load times for the user and
allow for a page to present a lot more information that the user can drill
down into quickly.
Element.load
What it does: As with Element.send, which essentially posts a form via
Ajax, this method allows you to update the contents of a DOM element
quickly with minimal code.
Usage:
$('myElement').load(url[, data]);
Example:
$('myElement').load('/page2.html');
160
MooTools Essentials

When you’ll use it: This handy shortcut allows you to acquire any element
from the DOM and update its content via Ajax. It’s very short and easy to
read and understand, and you’ll likely find yourself using it more often
than typing out new Request.HTML... etc.
Request.JSON
What it does: This class automates the sending and receiving of JSON
information (see “JSON” in Chapter 6).
Usage:
new Request.JSON(options);
Example:
//This code will send a data object via a
//GET request and alert the retrieved data.
var jsonRequest = new Request.JSON({
url: " /tellMeAge.php",
onComplete: function(person){
alert(person.age); //Alerts "25 years".
alert(person.height); //Alerts "170 cm".
alert(person.weight); //Alerts "120 kg".
}
}).get({'firstName': 'John', 'lastName': 'Doe'});
When you’ll use it: As outlined in Chapter 6, JSON is a transport language
much like XML, except that it uses native JavaScript notation. Using XML
to transport the data in and out of JavaScript requires you to crawl up and
down a document tree, while using JSON allows you to use dot notation (as
illustrated previously). Despite it being the “x” in Ajax, it’s actually
increasingly rare to use XML to manage data transactions from the browser
to the server.

MooTools Essentials
161

Chapter 11: Plug-Ins
MooTools, at its heart, is focused on making JavaScript more pleasant to
write. Making it easier to write well-designed code encourages reuse,
flexibility, and object-oriented principles.
Included in the library are several files that aren’t really part of this core
mission. These files certainly allow for interesting interfaces with drag and
drop, sortable lists, tooltips and more, but they aren’t really what
MooTools, to date, has considered its core mission.
This is why they are all lumped together and described as “plug-ins.” In
Chapter 12, I talk about plug-ins available from third parties. It is the
modular nature of MooTools itself that allows for the creation of plug-ins
with relative ease, and while MooTools contains many files it considers
plug-ins, this assignation should not imply that they aren’t great additions
to the library, nor that writing your own plug-ins is something you should
avoid. MooTools was built for extensibility, and to that end it illustrates
how to do it with its own plug-ins.
A More General Overview
Now that you’ve seen how to write classes and how to use them, I’m going
to spend a little less time on the classes in these next chapters than I have in
the previous ones. By now, you should have the hang of how to initialize a
class and pass it arguments and options, and how to invoke the methods of
that class and integrate those methods with actions and events on your site.
Consequently, I’m going to give an overview of all the MooTools plug-ins
here, but for the most part I’m going to direct you to the online
documentation and the demos of these classes so that you can see them in
action in the browser, so I can spend more pages here on real-world
examples (beginning in Chapter 13).

MooTools Essentials
163

Assets
The Assets set of classes automate the injection of assets into the
document (style sheets, images, JavaScript tags, etc.). Unless you’re doing
a lot of this in your document(s), it’s usually not worth using this script and
including its download weight. If you are injecting only one or two things,
you’ll do better to just use the Element constructor and injection methods.
The javascript and css methods all return an element object that has
already been injected into the document.
Assets.javascript
This is pretty straightforward:
var myScript = new Asset.javascript('/myscript.js', {
onload: function() {
//Call a function from myscripts.js
MyScript.start();
}
});
Assets.css
Pretty much the same thing as the preceding JavaScript example:
var myCSS = new Asset.css('/mycss.css');
Assets.image
Unlike the Assets.css and Assets.javascript methods, this method
does not inject the image into the document. It does, however, preload the
image.
164
MooTools Essentials

The way the interface works is that it takes a list of items and headers and
hides all but one of the items. When the user clicks a different header, it
simultaneously collapses the currently visible section while expanding the
section that corresponds to the clicked header.
Example:
new Accordion($$('dl#accordionExample dt'),
$$('dl#accordionExample dd'));
The first section displayed:

The second section, when clicked, expands as the first section closes:

The completed transition:

166
MooTools Essentials

Fx.Slide
This class slides the contents of an element in and out of view. It only
allows for sliding down like a window blind or sliding in from the left.

It accomplishes this by wrapping your content inside another div whose
overflow is hidden, and then moving the offset of your content negatively
up or to the left to “slide” it out.
Example:
var mySlide = new Fx.Slide($('myDiv'), {duration: 200});
mySlide.slideOut(); //My element slides out of view
//mySlide.toggle will slide back in now because it
//was hidden:
mySlide.toggle();
Fx.Scroll
This class smoothly scrolls the contents of any overflowed element (e.g., an
element with scrollbars), including the window. You can use it to smoothly
scroll back to the top of a window, to scroll to any x/y location, or to scroll
to any element on the page.

MooTools Essentials
167

Example:
var myScrollFx = new Fx.Scroll(document.body);
//Scroll to 300px from the top of the page:
myScrollFx.start(0, 300);
//Scroll down to the specified element:
myScrollFx.toElement($('myDiv'));
//Scroll to the top of the page:
myScrollFx.toTop();
Fx.Elements
This effects class works kind of like Fx.Morph in that it lets you alter
numerous CSS properties at once; however, in addition to this, it allows
you to alter numerous properties on numerous elements at once. If you
want to fade out three elements, while moving two others and fading out
another three, Fx.Elements will handle this transition more smoothly than
if you used Fx.Tween or Fx.Morph for each element.
Example:
var myFx = new Fx.Elements($$('div.animated'));
//Let's say there are 3 of these div.animated objects
myFx.start({
'0': { //Animate the first one from a spec to a square
height: [0, 100],
width: [0, 100]
},
'1': { //Resize the second one from a square to a spec
height: [100, 0],
width: [100, 0]
},
'2': { //Fade the third out to zero
opacity: 0
}
});
168
MooTools Essentials

Drag
The Drag class automates the work of tracking the movement of the mouse
and relating that movement to some value. Using Drag, you could alter the
color of the background of an element based on where the mouse moved.
You could alter the thickness of a border or iterate a counter up or down.
Its numerous options and events allow you to create any interaction based
on mouse movement that you can imagine.
Example:
//Create an Adobe Reader-style drag-to-scroll container
//that moves the contents of the page as the user drags
var myDragScroller = new Drag('myContainer', {
style: false, //Disable dragging by left/top style
invert: true,
modifiers: {x: 'scrollLeft', y: 'scrollTop'}
});
Element.makeResizeable
The only shortcut that comes with Drag.js is to make an element
resizable. Using this, you can allow the user to grab an element and drag to
make it wider, taller, or both. You can specify a “handle” that the user has
to click and drag. Otherwise, the user can click anywhere inside the
element and drag, and the element will resize.
Example:
$('myDiv').makeResizeable({
//An element inside acts as handle, not the whole div:
handle: $('myHandle'),
//The user can only resize vertically
modifiers: {x: false, y: 'height'} });

MooTools Essentials
169

Drag.Move
This class automates the interface interaction of dragging objects around. It
extends Drag to manage the process of relocating an element relative to the
movement of the mouse.
It has all the same options as Drag with the addition of two very useful new
ones:
container: A DOM element that the draggable element should be
constrained to; this will prevent the user from dragging the element outside of
a certain space.
droppables: A collection of DOM elements that are OK for the user to drop
the dragged element into. The events “over”, “leave”, and “drop” get fired on
the class with the dragged element as first argument when the dragged
element hovers, leaves, or get dropped on the droppable.
Example:
var myDrag = new Drag.Move('draggable', {
droppables: '.droppable',
onDrop: function(element, droppable){
if (!droppable)
console.log(element, ' dropped on nothing');
else
console.log(element, 'dropped on', droppable);
},
onEnter: function(element, droppable){
console.log(element, 'entered', droppable);
},
onLeave: function(element, droppable){
console.log(element, 'left', droppable);
}
});
170
MooTools Essentials

Element.makeDraggable
This is a shortcut method for making an element draggable. It accepts the
same arguments as Drag.Move.
Example:
$('myElement').makeDraggable({
droppables: '.droppable',
onDrop: function(element, droppable){ ... },
onEnter: function(element, droppable) { ... },
onLeave: function(element, droppable) { ... }
});
Color
The Color class is a utility plug-in that’s useful in altering color values.
Using it, you can add and subtract color values, making a given color
lighter or darker by mixing it with another color value. I personally don’t
find myself using it that much, but if you have a design that requires a
programatically defined color palette, this class can help you automate
calculating color values.
Group
This utility class allows you to group numerous items together and attach
events to them as a collection. For instance, if you want something to
happen only after the user has clicked numerous items, or if you want
something to happen when numerous Ajax requests complete, you can
group the objects together and attach a single event to the group.

MooTools Essentials
171

Example:
var xhr1 = new Request('/one.js', {
evalResponse: true
});
var xhr2 = new Request('abstraction.js', {
evalResponse: true
});
var xhr3 = new Request('template.js', {
evalResponse: true
});

var group = new Group(xhr1, xhr2, xhr3);
group.addEvent('onComplete', function(){
alert('All Scripts loaded');
});

xhr1.request();
xhr2.request();
xhr3.request();
//When all three complete, the alert will display
Hash.Cookie
I know what you’re thinking. You’re thinking about hash cookies. Well, I
hate to disappoint, but this class won’t give you a case of the munchies and
satisfy them. This combination of Cookie and Hash automates the creation
of a cookie containing a set of key values. It encodes the object into a query
string value (a JSON string, to be precise) and then evaluates it on retrieval.
This is more appropriate than having several cookies for storing user
preferences and the like, though it has the limitation of only supporting a
fixed amount of data (4KB is the limit).
172
MooTools Essentials

Example:
var fruits = new Hash.Cookie('fruit-colors', {
duration: 3600,
path: "/",
autoSave: true //Save on every operation
});
fruits.extend({
'lemon': 'yellow',
'apple': 'red'
});
fruits.set('melon', 'green');
fruits.get('lemon'); //yellow

// ... On another page ... values load automatically

var fruits = new Hash.Cookie('fruit-colors', {
duration: 365,
path: "/"
});
fruits.get('melon'); //green

fruits.erase(); // Delete cookie
Sortables
If you have a list that you need to allow the user to reorder, the Sortables
class takes most of the work out of the process for you. While it does
automate all the interaction and dragging and whatnot, it doesn’t actually
send any data anywhere as a result of the user changing the order. You’ll
have to integrate something like the Request class to send stateful
instructions back to the server for storage.
The Sortables class allows you to drag and drop inside a single list or
across several. This way users can reorder a single list, or reorder items
across lists with ease. You control this distinction by passing in a single list
element container or several.

MooTools Essentials
173

This class has many options, which allows it to be very flexible. The
examples on MooTools.net and in the online companion to this book
configure the class.
Example:
var mySortables = new Sortables('#list-1, #list-2', {
constrain: true,
revert: true,
onComplete: function(){
new Request({
url: '/dragManager.php'
}).post({
newOrder: this.serialize()
});
}
});
Slider
Thought it’s not that commonly used on the Web, the slider is certainly a
recognizable interface element appearing in desktop apps, the iPhone, and
car dashboards. MooTools gives us an easy class to drop in when we want
to implement this interface element into our own applications. The element
consists of a knob (that is dragged left-right or up-down) and the element
that contains (and therefore constrains) it. You can specify how many steps
are in the range and what happens when the user moves the knob.

Scroller
This class will scroll the contents of any overflowed element (including the
window) when the mouse approaches the edge of that element. This is very
174
MooTools Essentials

useful for drag-and-drop applications. If the user can drag an object from
one place to another, but the destination is out of view because it is scrolled
above or below, then you need some way for the user whose mouse is
engaged in dragging the item to scroll the window.
Consequently, this class is typically used in conjunction with Drag and
Drag.Move.
Tips
The Tips class automates tooltips. Give your elements a title property
for the title of the tip and a rel property for the description, and then
instantiate the Tips class.
Example:
<a href="/foo.html" title="The Foo Page"
rel="This link goes to the Foo Page"
class="tip">Go to Foo</a>
Code:
new Tips($$('a.tip'));
Result:

MooTools Essentials
175

Chapter 12: Third-Party Plug-Ins
As stated at the beginning of the previous chapter, the MooTools
framework has, to date, focused mainly on the core challenge of making it
easy and pleasant to write good JavaScript. While it contains a healthy
number of useful plug-ins, the framework itself is designed for
extensibility.
Consequently, numerous plug-ins are available on the Web for you to
download and use. Most of the plug-ins that are well written and well
documented follow all the patterns and conventions outlined in the
previous chapters. These plug-ins tend to provide a lot of options and
events to configure them, but regardless they are almost always classes that
can be extended and altered.
The CNET Clientside Libraries
For the last few years, I’ve been the principal JavaScript developer at
CNET Networks (despite the fact that my role there was never officially as
an engineer—I was a product manager). I left CNET in the fall of 2007 to
pursue my own startup, but I continue to contribute to the codebase that I
authored as well as blog about JavaScript and MooTools at
During the period that I spent authoring a lot of this code (and contributing
to MooTools), we at CNET decided to release as much of our JavaScript as
possible, and as a result we have a large number of plug-ins that have been
thoroughly tested and put into production on a heavily trafficked network.

MooTools Essentials
177

Here is a brief overview of some of the files that can be found there to date.
You can visit these libraries by going to the following URLs:
dbug
This wrapper for the Firebug console allows you to leave debug lines in
your code and “turn them on” only when you need them. In addition to
allowing you to leave information for yourself to inspect when something
goes wrong, it helps prevent the accidental publishing of code that contains
console instructions that will break in browsers without Firebug.
Browser.Extras
This extension adds numerous methods for managing URL data as well as
a class for launching pop-up windows.
Native Extensions
You’ll find extensions to String and Hash as well as a native Date object
that includes string parsing and date formatting methods.
Element Extensions
You’ll find methods for selecting text in form elements, computing the
actual size of elements, positioning elements relative to other elements, and
shortcuts like Element.hide and Element.show.
178
MooTools Essentials

Effects Extensions
Fx.Reveal will automatically and smoothly transition an element whose
display style is set to “none” to “block”, expanding the element and fading
it in. It’s a less abrupt method than just changing the display from “none”
to “block” (or vice versa).
Fx.Move allows you to move an element from one location to a location
relative to another (e.g., move this element on top of, or below, or to the
right of some other element).
Fx.Sort allows you to reorder a list of elements smoothly; they all move
to their new locations instead of just jumping to them.
Fx.Marquee helps automate a marquee effect so you can repeatedly show
messages with different transitions.
Request
The JsonP class allows you to send and receive data to a remote server on
a different domain, a limitation that Ajax doesn’t allow. This has the
potential to be insecure, so you should be sure to send and receive data to
and from servers that you control and trust.
UI
The CNET Clientside Libraries have over a dozen interface classes,
including the following:
  IconMenu: An icon carousel that allows the user to paginate through a
horizontal or vertical list of items.
  Modalizer: A class that creates a “modal” layer that overlays the contents
of the window with a semitransparent layer; this is integrated with our
StickyWin class, detailed later in this list, to create dialogs that gray out the
page content until they interact with the dialog.

MooTools Essentials
  179

  PopupDetails: A class that creates an interface of tooltip-like displays with
rich details. For instance, if you have a lot of products displayed, you can
show rich metadata when the user mouses over the image of the product.
  StickyWin.alert: A replacement for alert() that looks a little nicer and
doesn’t freeze the browser.
  StickyWin: An in-page DHTML pop-up manager for pop-up messages and
forms. This highly configurable and flexible, draggable, resizable UI element
can be used for nearly any pop-up interaction.
  Waiter: A class that overlays a DOM element with a semitransparent layer
and a spinning Ajax indicator to illustrate to users that there is some sort of
transaction occurring that they must wait for. The class can be used on its
own, but it is also integrated into the Request classes so that you can enable
it with a single option passed when you create a Request instance. When the
request is running, the waiter is displayed.
Layout
The CNET Clientside Libraries feature a few classes designed to animate
layouts or facilitate creating them on the fly (like data tables).
  HtmlTable: This automates the building of an HTML table from a data set,
allowing you to add rows on the fly.
  MultipleOpenAccordion: This is very similar to the Accordion class in
MooTools except that it allows the user to open more than one section at a
time.
  MooScroller: This class re-creates the traditional scroll interface for
overflowed elements using DOM elements that can be styled.
  SimpleCarousel: This class offers a simple carousel interface with slides
and buttons that show the corresponding slide. It can also automatically cycle
through the slides until the user interacts with it.
  SimpleSlideShow: This class creates a simple slide show with previous
and next buttons.
180
MooTools Essentials

  TabSwapper: A common interface element, the “tabbed box” allows users to
click tabs above a set of content elements to see the corresponding element.
Forms
CNET builds a lot of internal tools, and consequently we have a lot of
JavaScript tools for making managing content more pleasant. Here are a
few of them:
  DatePicker: A flexible date selector that lets the user choose from a
calendar of dates, this class can be configured to allow for selecting a single
date or a date range, as well as entering a specific time.
  FormValidator: This class is a nonintrusive form validator. After assigning
the inputs of a form various CSS classes, you can instantiate this class to give
validation errors to users as they interact with the form, saving them the
trouble of having to submit the form to get errors. It also allows for custom
validation rules.
  OverText: This class will take the alt or title text for an input and display it
over the element when it has no value. This allows you to give a contextual
element to empty inputs. When the user clicks into the element, the text is
hidden. If the user clicks out without entering any values, the text returns. The
text itself is a DOM element positioned above the input that can be styled
however you like. It is not actual input text, so it won’t be submitted
accidentally by the form.
  SimpleEditor: This class creates a simple HTML editor. It is not a
WYSIWYG editor, but instead offers buttons to wrap selected text with
HTML tags or else prompts the user to fill out the attributes of a tag (like an
image tag).
This isn’t a complete accounting of all the scripts Clientside has to offer,
but it should give you an idea of what’s there.

MooTools Essentials
  181

Other Third-Party Scripts
The collection of CNET’s Clientside scripts I outlined in the previous
section aren’t the only plug-ins available. There are numerous other authors
out there who have released plug-ins. Most of these plug-ins can be found
browsing to the “Your Scripts” category. Here various users have
submitted their own scripts for members of the MooTools community to
use and provide feedback.
Some of these are hit or miss. A good indication of a good script is how
well documented it is and whether it has numerous examples that you can
see in action.
Note
As of this writing, the MooTools forums have moved to a Google
forum, however, is still there (in read-only mode) and features all the
scripts I refer to earlier, so it’s still worth digging into. The MooTools team is
currently working on a plug-in page to feature other third-party plug-ins, so
check the MooTools site for updates.
Of the scripts available in this section, I have used only a few, described
next.
Autocompleter, FancyUpload, ReMooz, SqueezeBox, Roar
Harald Kirschner (a.k.a. digitarald) is another contributor to MooTools and
you can find the following classes, all of which I recommend trying out:
Autocompleter: This is an autocompletion class that works with local data
in memory (e.g., an object defined in the page), Ajax, or JSON. Note that I
have integrated CNET’s JsonP class with Autocompleter and provided
182
MooTools Essentials

a copy in the CNET libraries. I’ve also documented all the options
which, as of this writing, Harald hasn’t gotten around to yet.
  FancyUpload: Swiff and Ajax come together for an elegant upload interface
that displays the progress of any number of files being uploaded to the server.
  ReMooz: This image gallery–like plug-in lets users zoom in on thumbnails
and get a high-quality version of the image.
  Roar Notifications: This notification widget streamlines incoming
messages for updates or errors, adding only minimal distraction to the
interface.
  SqueezeBox: This Lightbox-inspired pop-up allows you to embed just about
anything from images to Flash videos in an in-page pop-up.
  History: This class adds back-button functionality to Ajax-applications. It
provides a history-change event and a dynamic routing to manage several
widgets in one page.
Slimbox
This is a clone of Lightbox, a slide show built for script.aculo.us and
syntax (with a refactoring of the effects queue and other parts), but it didn’t
actually create a MooTools class out of it. Instead, it works like the
Prototype version does, which is a collection of methods into the Lightbox
namespace.
The downside of this conversion is that it’s not a class, so it’s not possible
to have more than one instance, it doesn’t have configurable options or
events, and you can’t extend it.
Finally, the other issue with the library is that it hasn’t been updated for
MooTools 1.2 by the original converter. Consequently, you’ll find a new

MooTools Essentials
  183

version in CNET’s library that does all this, though the credit for it all still
belongs to the original author of Lightbox, Lokesh Dhakar (who wrote
Lightbox for Prototype.js) and Christophe Beyl (who first ported it to
MooTools).
. . . And More
I don’t spend a lot of my time digging around in the forums for plug-ins
that people post, but there are a lot of them to play around with. If you’re
looking for something that seems like the kind of thing someone else would
have made (date pickers, form validators, pop-ups, etc.), chances are
someone did. Actually, chances are that several people did and there are
several versions for you to choose from, so I encourage you to dig around
in the “Your Scripts” section of the MooTools forum when you have the
time.
184
MooTools Essentials

Chapter 13: Real-World Examples
The bulk of this book up to this point is designed to help you learn the
purpose of various methods and classes in the MooTools library. It’s
possible, through reading about these methods and classes and looking at
the examples, to glean the “MooTools way” of doing things. As outlined at
the beginning of this book in “About MooTools” in the Introduction, the
following goals are part of MooTools’s core mission:
  Don’t duplicate code.
  Add functionality that fits in principle with JavaScript’s own design
philosophy.
  Extend native objects (String, Function, Array, Element, Event, and
Number) as JavaScript was designed to do.
  Write clean, clear, well-named code that is understandable when read by
anyone with the skills to understand it.
  Abstract as much away from the browser as possible.
  Whenever possible, make it still feel like you’re writing JavaScript.
  Make it modular.
These aren’t all the points outlined in the Introduction, but they are the
pertinent points to what I’m going to cover next: the code you write.
MooTools is a framework that makes authoring JavaScript easier and better
in many ways, but you still need to write your own code to add
functionality to your pages. If you include the MooTools library on your
pages, absolutely nothing will happen unless you write code creating
instances of effects, Ajax, and more.
So let’s take on some real-world examples of how to author JavaScript in a
“MooTools way.”

MooTools Essentials
  185

A Simple Page
As the section “Adding MooTools to Your Page(s)” in Chapter 1
illustrates, adding the MooTools library to your pages is pretty
straightfoward. You download the library and save it to the directory with
the rest of your web assets and then reference it with a script tag:
Let’s imagine that we want to attach a simple event to all the links on the
page to load the content each points to into a container. In this example, we
can see the DomReady custom event (see Chapter 6) in use, the get and
addEvent element methods (see Chapter 5) in use, an instance of Request
(see Chapter 10) to fetch data from the server, the native Event class (see
Chapter 4) to stop the link clicks, as well as selectors (see Chapter 6) and
array iteration (see Chapter 4). We’ll pick apart the code line by line after
the full example that follows.
186
MooTools Essentials

Dissecting the Example
Let’s look at the preceding example line by line. I’m only going to focus on
the JavaScript, as the HTML is pretty straightforward.
First, we can’t reference anything in the DOM until it’s there, and our
script tag, at the top of the page in the head, will be interpreted before
the rest of the HTML loads. We use the addEvent method on the window
to wrap our functionality in the DomReady event so that our code will be
executed as soon as the HTML is loaded (but it won’t have to wait for
images and whatnot to load).
window.addEvent('domready', function(){
Now that it’s safe to reference the DOM, we can select the links we want to
modify. We use the $$ method to select all the links in the pageLinks div.
We’ll need Selectors.js in order for this to work because $$ accepts
only tag names unless you include this script in your copy of MooTools.
With it you can specify a CSS selector.
$$('#pageLinks a').each(function(link){
//Can be also written as
$('pageLinks').getElements('a').each(...
Here we see an example of function chaining. This is when we execute a
method on the object returned by another function (this shouldn’t be
confused with the Chain class). All this means is that if a function returns a
string, you can invoke the function and then execute a string method on
the result. For example, $('myElement').setStyle(...) invokes the $
method and then invokes the setStyle method on the element returned by
it. setStyle is a property of Element, not of $. So in the preceding
example, we invoke $$, which always returns an array (even an empty one
if it doesn’t find any elements that match the selector), and then we invoke
.each, which is a property of Array.
188
MooTools Essentials

Array.each accepts two arguments: the item in the array being iterated
over and the index of that item in the array. In our example, we don’t need
to reference the index, so we don’t have to declare it, but we could if we
wanted to.
Next, we take the link that is passed to our function and add an event to it
for when the user clicks it:
link.addEvent('click', function(event){
We specify which event to monitor (click) and pass a function to be
executed when the user clicks it. This function is anonymous (i.e., it is not
declared as a variable with a name, it’s just a literal function(){} object)
and accepts as its argument the event that is created when the user clicks
the link. This is an instance of the Event class.
Next, we prevent that event from doing what would normally happen if the
user were to click the link (i.e., the page would load the URL as a new
document). We don’t want this to happen; we want to update a portion of
the page with the contents of the URL that the link points to, so we use the
preventDefault method so that the link click doesn’t load a new page.
event.preventDefault();
Finally, when the user clicks the link, we want to update the div that holds
our page information with the contents of that URL. We could create a new
instance of Request to update the content, but the element shortcut load
will work just fine here; no need to write more code than we need. This
method accepts a URL that we need to retrieve from the link, which we do
with element.get.
$('pageContainer').load(link.get('href'));
}); //End the addEvent statement
}); //End the each iteration
}); //End the domready statement

MooTools Essentials
189

Note
Whenever you load content into a page this way, the URLs you
request should not be entire documents; they shouldn’t have head and
body tags but instead should be HTML fragments. Whatever is returned by
these URLs will be injected in their entirety into the document. This means
that if your site has a logo and navigation bar layout, and the links you
point to also have this, you’ll see those elements loaded into your container.
This is why you should just return the content that you would want to exist
in the updated DOM container and nothing else.
Summary
This simple example strings together numerous native methods
(Element.addEvent, Element.get, Element.load, Array.each, and
Event.preventDefault), stand-alone methods ($$), and classes
(Request) to add some nice functionality to our pages—all in just eight
lines of readable code.
But adding functionality in this manner will only get you so far, which is
why you need to write classes. You’ll see an example of how to do so in
the next chapter.
190
MooTools Essentials

Chapter 14: Writing a Tab Class
In the example in Chapter 13, we had some HTML with four links to
different pages, followed by a container that would display the contents of
the pages those links pointed to. We implemented the previous example to
select a specific group of links on a specific page, but what if our site had
lots of these things? What if we had a dozen pages, each with three or four
different placements of this layout? Writing the same chunk of code over
and over again wouldn’t be very efficient.
Instead, we should turn the pattern into a class, which we can initialize over
and over again for each placement, passing in only the variables that make
each one unique.
By making a piece of interaction into a class, we can maintain a state and a
reference to various objects for effects, Ajax, or DOM elements. We can
define methods that we can use to manipulate that state whenever we like.
Finally, the resulting chunk of functionality can be extended to add more
functionality later. All this adds up to resuable code that can save us a lot of
time. For example, if you find a bug in your code, you fix it in one place,
and every place that uses it is fixed, so you don’t have to hunt down all the
places where you’ve written the functionality and fix it in each one.
So let’s write a class for the pattern we have in our example from Chapter
13. Our objective here will be to end up with the exact same result, but
instead we’ll be able to reuse it and extend it.

MooTools Essentials
191

Step 1: Creating an Empty Class
When writing a class, you’ll almost always start out the same way:
var AjaxTabs = new Class({
Implements: [Options, Events],
options: {},
initialize: function(){}
});
This template is the very basics of a class. Any class that you’re going to
use more than once is going to have options (see Chapter 8), and any class
that the user can interact with (or otherwise has functionality that happens
at arbitrary times—like effects or Ajax) will likely have events. Any class
that should do something when you instantiate it will have an initialize
method.
Because we started out this excercise with the specific goal of reproducing
our example from the previous class, I’m going to remove the options and
events lines from this example, but they’ll show up again as we progress.
This leaves us with the following:
var AjaxTabs = new Class({
initialize: function(){
}
});
Step 2: Defining Arguments
In our case, we can start off knowing what the variables are by looking at
the example we’re trying to emulate from the previous chapter. We know
we’ll have links to different HTML fragments (the “pages”) as well as a
container where those fragments go. Our class can’t work without these
things, so we’ll make them arguments.
This is the key distinction between arguments and options: options are just
that—optional—while arguments are required for the class to work.
192
MooTools Essentials

Sticking with this pattern will help anyone else who uses this class
understand the distinction (and it’ll help you, too, when you use it again
after a few months pass). Being consistent with arguments versus options
make it less likely that your class will break when someone else uses it.
So let’s change our template by adding our arguments and storing them.
I’ve emphasized the changes in bold here, which we’ll dissect after the
example. Again, we won’t have options in this example yet, but they’ll
show up later.
var AjaxTabs = new Class({
initialize: function(container, links){
this.container = $(container);
this.links = $$(links);
}
});
The bold changes now specify that our class accepts two options: a
container (where the updated content goes) and links (the page links).
Dissecting this a bit, we have the following:
First, we store the container reference as a property of the class. This way
we can reference it later. We also wrap the reference with the $ method.
This serves several purposes: it allows the user to pass in an element’s ID
(a string) or the element reference itself. It also ensures that that element is
properly extended with MooTools methods.
this.container = $(container);
Then we store the links. This array of links gets passed through $$, which
serves the same purpose as the previous line being passed through $. The
user can pass in an array of links or a selector to retrieve those links. If the
user passes in an array of elements, we ensure that this array of elements is
extended with MooTools by passing it through $$. In both cases, it won’t
matter if the elements have already been passed through $$ or $—there’s
no real expense to doing it twice.

MooTools Essentials
193

this.links = $$(links);
So now our class can be initialized, and the values stored in it can be
referenced. If we did create an instance now, it wouldn’t do anything
except store these references. Here’s what that would look like:
var myAjaxTabs = new AjaxTabs($('pageContainer'),
$$('#pageLinks a'));
myAjaxTabs.container //The $('pageContainer') div
myAjaxTabs.links //The four $$('#pageLinks a')
//link elements
Now we need to actually do something with this information.
Step 3: Defining Methods
Our class now has stored references to the container and the links, but we
need to actually add some behavior to them in order for our class to
actually have an effect. Let’s add some methods to our class.
var AjaxTabs = new Class({
initialize: function(container, links){
this.container = $(container);
this.links = $$(links);
this.attach();
},
attach: function(){
this.links.each(function(link){
link.addEvent('click', function(event){
event.preventDefault();
this.container.load(link.get('href'));
}.bind(this));
}, this);
}
});
Cool. Now we have a class that, when initialized, will make the links
passed in to it load their contents into the container specified. We’ve now
duplicated the code we started out with. Granted, it’s twice as many lines,
194
MooTools Essentials

but now we have something we can reuse and build upon. Let’s dig into the
new lines.
In the initialize method, we reference another method in the class:
this.attach();
The this keyword is very important. It references the instance of the class.
So if on our page we create three instances, each instance can refer to itself
as “this” and not run into the other instances. This is a really powerful
concept, as it allows these little buckets of functionality to keep track of
their own state. When you get the hang of using the this keyword, you’ll
see how it lets you make really clean code, even if you have a lot of this
references all over the place, as evidenced in our attach method:
attach: function(){
This method, which is a property of every instance of our class, has no
arguments. We could have specified some, but we don’t need to since we
stored our references to the links we want to monitor as this.links.
this.links.each(function(link){
We iterate over the links using the array method each as we did in our
example in the previous chapter, but there’s a difference here: each can
take two arguments. In our previous example, we only used the first (a
function to invoke with each item in the array), but not the second—an
object to bind the this keyword to.
By default, the function you pass to an array in its iteration methods is
bound to that array, so the this in the function references the array. But
here we need this to reference our class so we can continue to reference it.
So if we jump ahead to the end of this statement, we see
this.links.each(function(link){
...
}, this);

MooTools Essentials
195

By specifying this second argument as a reference to our class, the function
can reference this and point not to the array of links, but instead to our
class. This is a little tricky, but it’s very important (see “‘this’ and Binding”
in the Appendix for more detail).
Inside our iteration, we add the event to the link just as we did in the
previous chapter, but again, we have a subtle difference. Just like
Array.each, Element.addEvent accepts as one of its arguments a
function to invoke when the event is fired. If we want the contents of this
inner function to be able to reference the this that refers to our class
instance, we need to bind it to the function.
Unlike the array iteration methods, addEvent doesn’t accept an additional
argument for binding, so we must use the bind method on the function
itself:
link.addEvent('click', function(event){
...
}.bind(this));
This is one of those gotcha things. Array and Hash iteration methods allow
you to specify an argument for binding, but element event methods do not.
Why doesn’t MooTools make this consistent? Well, it’s because the
standards defined for JavaScript say otherwise, and where possible,
MooTools follows those standards. Note that
myArray.each(function(){...}.bind(this))
will work, though it’s not the “proper” way to do it. Moving on . . .
The last bit of code inside our click event looks very similar to the
original example, with the only difference being that now we reference the
container as this.container. It’s because of this reference that we have
to do the binding in the previous two lines. So, if you don’t reference
this inside an inner function, you don’t need to bind anything to it.
196
MooTools Essentials

link.addEvent('click', function(event){
event.preventDefault();
this.container.load(link.get('href'));
}.bind(this));
Instantiating Our Class
OK, so now we have a class that does what the previous example did. Now
what? Just having a class doesn’t do anything—you have to instantiate it.
So our new page would look like this:
});

MooTools Essentials
197

window.addEvent('domready', function(){
new AjaxTabs($('pageContainer'),
$$('#pageLinks a'));
});
</script>
</head>
<body>
<ul id="pageLinks">
<li><a href="/page1.html">page 1</a></li>
<li><a href="/page2.html">page 2</a></li>
<li><a href="/page3.html">page 3</a></li>
<li><a href="/page4.html">page 4</a></li>
</ul>
<div id="pageContainer"></div>
</body>
</html>
Review
First, I’ll again note that including all your JavaScript in the page like this
isn’t a best practice. You should include most of your code—especially
reusable classes—in an external .js file. I’m putting it in the page here just
to make the example easier to read.
We created a class that updates our page with the contents of the link URLs
when clicked, and we can reuse that class in as many places as we want. As
I outline in Chapter 1 in the section “Coding for Reuse,” I prefer to think of
the code I write in two ways: implementation code and reusable code. The
preceding example highlights these two principals quite clearly: our class is
designed to be reused and extended, and we could really use it anywhere
we wanted to.
Classes, however, don’t do anything unless you invoke them. Invoking a
class is something you do with specific variables passed to them to
configure them for a specific use, as with our example here where we
198
MooTools Essentials

create a new instance of our class with the links and container on the page.
This code isn’t reusable at all—it’s quite specific to this page. When you
build your site, your implementation code should be very light and as
limited as much as possible to the things that are specific to a given page or
a page’s components, while the code that is shared across your site should
be filled with classes that manage these components when they are
initialized.
If you treat all the layout elements on your page this way, you’ll end up
with a much more manageable codebase as well as code you can reuse that
you perhaps hadn’t planned on reusing. It’s actually quite common for me
to write a class for a layout component thinking I’ll never use it for
anything else, only to find myself coming back to it to extend it for some
other use. With that in mind, we’ll make our class a little more flexible and
extend it for greater reuse in the next chapter.

MooTools Essentials
199

Chapter 15: Writing Flexible Classes
In the previous chapter, we wrote a class that featured a number of links
that, when clicked, would update the contents of a container on the page. If
we were to add a little bit of CSS styling, we might lay out the contents so
it appears in a browser like this:

This pattern—tabs essentially—is one that’s used a lot on web sites these
days in lots of configurations. Look, here’s Yahoo’s home page:

MooTools Essentials
201

If we wrote our AjaxTabs class a little more generically, maybe it would
be more broadly useful. The question then is what things do we need to be
able to configure for it to behave differently in different use cases?
Well, for starters, what if we didn’t want to use Ajax to get the content?
What if we wanted to let the user click a tab and just show the appropriate
container of content that’s already loaded on the page? Sure, if we need to
fetch the information with Ajax, that should be an option, but if we already
have the information, we shouldn’t go get it again. So let’s take the Ajax
out of our little class, and then extend it so we can put the Ajax back in.
Also, while we’re at it, let’s add some options and events so we can
configure our pages in ways that we might need to.
202
MooTools Essentials

Step 1: Creating a Foundation Class
Starting with our example from the beginning of this chapter, let’s re-create
our tab class without the Ajax. Unlike the previous chapters, I’m not going
to dissect the example line by line (as our code examples are going to start
getting somewhat long). Instead, I’ll include comments in the code briefly
describing what each line is for.
A preface to this new version of the example: unlike the previous version,
which used Ajax to update the contents of a single container, we’re going
to make this version hide and show the container that corresponds to the
tab the user clicks. So if we have four tabs, we’ll have four containers. If
the user clicks the first tab, we’ll show the first container and hide the
others. Also, since we aren’t fetching information via Ajax, we won’t
assume that the tabs are links, though they could be.
var Tabs = new Class({
//We are going to store our tabs in an array that's
//a property of the class - previously we called them
//links, but they don't have to be anchor tags
//anymore, so we'll be more generic with our name
tabs: [],
initialize: function(containers, tabs){
//We need to make sure that the containers
//and tabs are an Elements collection
//so we pass them each through $$
containers = $$(containers);
//For each tab passed in, we'll iterate over it
//and pass both the tab and the corresponding
//container to our new method that adds sections for
//us
$$(tabs).each(function(tab, index){
this.addSection(tab, containers[index]);
}, this);
this.show(0); //Show the first tab on startup
},

MooTools Essentials
203

//Include the tab in the tabs array; use
//.include in case for some reason, it's already
//in there
this.tabs.include(tab);
//Store a reference between the tab and its
//container
tab.store('container', container);
//Pass the tab to our attach method
this.attach(tab);
},
//Our attach method has changed; now it takes
//as its argument a single tab to monitor
attach: function(tab){
tab.addEvent('click', function(event){
event.preventDefault();
//And we send the instruction to display a
//tab's content to a new "show" method, which
//can be invoked at any time, not just here
this.show(this.tabs.indexOf(tab));
}.bind(this));
},
//Our show method takes the index of the item to show
show: function(index){
//At the end of this method we store the index that
//is currently visible. If this method is called to
//show the tab that's already visible, don't do
//anything.
if (this.current === index) return;
//We iterate over each tab
this.tabs.each(function(tab, i){
//If the index we're showing matches the index of
//the tab we're iterating over, then we set its
//display style to block, otherwise we set it to
//none to hide it
var container = tab.retreive('container');
if (index === i)
container.setStyle('display', 'block');
else container.setStyle('display', 'none');
204
MooTools Essentials

});
this.current = index;
}
});
And here’s what it would look like to invoke this class:
<script>
window.addEvent('domready', function(){
new Tabs($$('#tabContainers div.container'),
$$('#tabs li'));
});
</script>
//The HTML for it would look something like this:
<ul id="tabs">
<li>Tab 1</li>
<li>Tab 2</li>
<li>Tab 3</li>
</li>
<div id="tabContainers">
<div class="container">This is the content
for the first tab.</div>
<div class="container">This is the content
for the second tab.</div>
<div class="container">This is the content
for the third tab.</div>
<div class="container">This is the content
for the fourth tab.</div>
</div>
So this is our “foundation” class. It does all the basics of a tabbed interface,
but there are three big things missing: options, events, and the ability to
load the content via Ajax (which is where we started).
A Note on Using Methods
A quick thing to note that’s new in this class from the previous chapter is
the show method. Because we now have a method to show a specific tab,

MooTools Essentials
205

we could, in theory, change the tab at any time by referencing this method.
For instance, let’s say we had another link on the page somewhere and we
wanted to change to the second tab if the user clicked it. We could do
something like this:
var myTabs = new Tabs($$('div.container'),
$$('#tabs li'));
$('myOtherLink').addEvent('click', function(){
myTabs.show(1); //Switch to the second tab
return false; //Stop the event from propagating
});
This ability to reference the methods of the instance is obviously really
useful. It allows you to create an instance of a class and then invoke the
behaviors in that class when you need to. When you are authoring a class,
consider how and where you’ll want access to functionality like this and
make these methods easy to use.
Step 2: Adding Options
Whenever you have a class that’s designed to be used over and over again,
it’s almost always a good idea to identify the things in the class that you
might want to tweak for a given implementation. Regarding the preceding
code, here are some things we might want the class to allow us to do when
we create instances of it:
Add a CSS class to the selected tab and selected section.
Specify a different “start” index (right now, the first tab is shown on startup).
There are potentially a lot of other things you might want to configure. You
could make the sections fade in and out with effects. You could store a
cookie with the state of the tabs so that it restores itself for users when they
visit the page again. For our purposes, let’s keep things simple and just add
these two options: a CSS class for the selected tabs and sections, and the
ability to specify a different start option.
206
MooTools Essentials

Here’s our class again, this time without all the earlier comments and with
a few new lines I’ve emphasized in bold and commented about.
var Tabs = new Class({
  //Add the functionality of the Options class
//to our class
Implements: Options,
options: {
//The default value of our options
//If we don't specify any of these, the
//default values are used
selectedTabCssClass: 'selected',
selectedSectionCssClass: 'selected',
firstShow: 0
},
tabs: [],
  //Our constructor now takes a 3rd argument: options
initialize: function(containers, tabs, options){
  //Merge the options passed in by the user with those
//defined by the class; note that it's OK if this
//argument is undefined
this.setOptions(options);
containers = $$(containters);
$$(tabs).each(function(tab, index){
this.addSection(tab, containers[index]);
}, this);
  //Show the panel specified in the options
this.show(this.options.firstShow);
},
addSection: function(tab, container) {
this.tabs.include(tab);
tab.store('container', container);
this.attach(tab);
},

MooTools Essentials
  207

attach: function(tab){
tab.addEvent('click', function(event){
event.preventDefault();
this.show(this.tabs.indexOf(tab));
}.bind(this));
},
show: function(index){
if (this.current === index) return;
this.tabs.each(function(tab, i){
var container = tab.retreive('container');
//If we're showing the tab, add the CSS classes,
//else remove them
if (index === i) {
tab.addClass(this.options.selectedTabCssClass);
container.addClass(
this.options.selectedSectionCssClass);
container.setStyle('display', 'block');
} else {
tab.removeClass(
this.options.selectedTabCssClass);
container.removeClass(
this.options.selectedSectionCssClass);
container.setStyle('display', 'none');
}
}, this); //Now we're using 'this' inside this
//funciton, so we must specify a binding
//here to keep 'this' pointed to our
//instance.
this.current = index;
}
});
Adding options is pretty easy. You shouldn’t go crazy with them, but in
general, any place you can conceive of wanting to change a value for a
specific instance is where you should add an option.
Let’s look at how we’d invoke this class and specify different options.
208
MooTools Essentials

the user drops what he or she has been dragging—we need a hook into that
moment.
The Events class, not to be confused with the native Event class that
extends the native browser event created when users click, mouseover, etc.,
allows us to add events to our classes so that these unpredictable moments
have the hooks we need to manage the behavior we want.
Making Good Use of Events
Like options, we want to use events judiciously. There’s no expense to
having too many other than your code getting bloated, but at the same time
we want to be able to quickly use our classes, so choosing the key points
where an event is needed is important.
The other key to using events is passing the best arguments to the event
when it is fired. Not only must you choose the best places to add events,
but you also need to decide which values to pass, since when you fire an
event, you can pass any number of values to it. This is important because
you need to be able to do something with the event when you add hooks
into the class. Let’s reconsider the Ajax example we just discussed.
Knowing that the server has returned something is only half the battle—we
need to know what the server returned.
So with our tab layout class, what events occur that we might want to know
about? Well, when the user clicks a tab, the tabs change. That might be
useful information. What would we want to know when this occurs?
Certainly, we’d want to know what tab is now currently visible. Maybe
we’d also want to know which tab just got hidden? Given that we do these
two things separately as we iterate over all the tabs, we can’t have a single
event, so instead we’ll have to fire them each off separately—one for when
a tab is shown, and another for when a tab is hidden.
210
MooTools Essentials

Again, here’s our class in its current form with the new code in bold:
var Tabs = new Class({
//We're implementing two classes in now,
//so we must use an array to specify both
//items to be implemented
Implements: [Options, Events],
options: {
selectedTabCssClass: 'selected',
selectedSectionCssClass: 'selected',
firstShow: 0,
//Our class now has two events that you can specify
//in the options
onShow: $empty,
onHide: $empty
},
tabs: [],
initialize: function(containers, tabs, options){
this.setOptions(options);
containers = $$(containers);
$$(tabs).each(function(tab, index){
this.addSection(tab, containers[index]);
}, this);
this.show(this.options.firstShow);
},
addSection: function(tab, container) {
this.tabs.include(tab);
tab.store('container', container);
this.attach(tab);
},

attach: function(tab){
tab.addEvent('click', function(event){
event.preventDefault();
this.show(this.tabs.indexOf(tab));
}.bind(this));
},

MooTools Essentials
211

show: function(index){
if (this.current === index) return;
this.tabs.each(function(tab, i){
var container = tab.retreive('container');
if (index === i) {
tab.addClass(this.options.selectedTabCssClass);
container.addClass(
this.options.selectedSectionCssClass);
container.setStyle('display', 'block');
  //We must add the instruction to invoke, or
//"fire," the event in our code where we think
//is the most suitable time; here we fire it
//after the container has been displayed
this.fireEvent('onShow', [i, tab, container]);
} else {
tab.removeClass(
this.options.selectedTabCssClass);
container.removeClass(
this.options.selectedSectionCssClass);
container.setStyle('display', 'none');

  //If the current tab is the one we're iterating
//on OR there is no currently visible tab
//(because this is the first time we've called
//this method), then fire the 'onHide' event
if (this.current === i || !$chk(this.current))
this.fireEvent('onHide', [i, tab, container]);
}
}, this);
this.current = index;
}
});
Now our class has events for both when a tab is displayed and when one is
hidden. Note that in both cases we pass as arguments the index, the tab, and
the container that have just been shown or hidden.
212
MooTools Essentials

So let’s look at what it’s like to actually use these events. Let’s say we
want to show a tooltip when the user shows the fourth tab; maybe it has a
form in it. The tooltip is out of context when the other tabs are displayed,
so we need to show the tooltip when the fourth one is displayed, and hide it
when the fourth one is hidden.
window.addEvent('domready', function(){
new Tabs($$('#tabContainers div.container'),
$$('#tabs div.tab'), {
//The function that's called when the event fires
//is passed the index, the tab, and the container:
onShow: function(index, tab, container){
//If the fourth one is shown, show my tip
if (index == 3)
$('tip').setStyle('display', 'block');
},
//Hmmm. Here we’re not using the tab and container
//references. We can save a few keystrokes and just
// not declare them; there's no harm if we do,
//but we’re not using them so we’ll skip them:
onHide: function(index) {
//If the fourth one is hidden, hide my tip
if (index == 3)
$('tip').setStyle('display', 'none');
}
});
});
Adding Events After Invokation
In the preceding example, we create an instance of our tabs class and
specify the onHide and onShow events in the options. This is some magic
that’s provided by the Options class. If it finds an option that begins with
“on” and the value is a function, it’ll treat it as an event. Note that when it
encounters options like this, it removes them from the options object when
it sets up the events.

MooTools Essentials
213

But you can also use the addEvent method to attach your events after
you’ve instantiated your class. This can be especially useful if you end up
with more than one function that needs to be invoked when an event fires.
The sytnax is the same for classes as it is for elements:
myTabs.addEvent('onShow', function(index, tab,
container){ ..... });
You Don’t Have to Declare Events in the Options Object
In our class, the options with events look like this:
var Tabs = new Class({
Implements: [Options, Events],
options: {
selectedTabCssClass: 'selected',
selectedSectionCssClass: 'selected',
firstShow: 0,
onShow: $empty,
onHide: $empty
},
...etc
In the options, we declare that the onShow and onHide events default to
$empty, which is just an empty function. Because the Options method
setOptions removes these values from the options object, you don’t really
have to declare them like this. There’s no benefit. It doesn’t hurt anything,
but it doesn’t get you anything.
Still, it’s nice to be able to glance at the code and see what the options and
events are, all right there at the top of the class. By convention, MooTools
leaves these lines in the source code but comments them out. So if you look
at any class in the MooTools library, you’ll find these declarations present,
but commented. This is a good practice (as it cuts down on your code size,
even if only a little), and I follow it in my own code.
214
MooTools Essentials

So, taking my own advice, our finished “foundation” class would look like
this:
var Tabs = new Class({
Implements: [Options, Events],
options: {
selectedTabCssClass: 'selected',
selectedSectionCssClass: 'selected',
firstShow: 0 //Don't forget to remove the trailing
//comma here as it's now the last
//item in this object
/* onShow: $empty,
onHide: $empty */
},
tabs: [],
initialize: function(containers, tabs, options){
this.setOptions(options);
containers = $$(containers);
$$(tabs).each(function(tab, index){
this.addSection(tab, containers[index]);
}, this);
this.show(this.options.firstShow);
},
addSection: function(tab, container) {
this.tabs.include(tab);
tab.store('container', container);
this.attach(tab);
},
attach: function(tab){
tab.addEvent('click', function(event){
event.preventDefault();
this.show(this.tabs.indexOf(tab));
}.bind(this));
},

MooTools Essentials
215

show: function(index){
if (this.current === index) return;
this.tabs.each(function(tab, i){
var container = tab.retreive('container');
if (index === i) {
tab.addClass(this.options.selectedTabCssClass);
container.addClass(
this.options.selectedSectionCssClass);
container.setStyle('display', 'block');
this.fireEvent('onShow', [i, tab, container]);
} else {
tab.removeClass(
this.options.selectedTabCssClass);
container.removeClass(
this.options.selectedSectionCssClass);
container.setStyle('display', 'none');
if (this.current === i || !$chk(this.current))
this.fireEvent('onHide',
[i, tab, container]);
}
}, this);
this.current = index;
}
});
Step 4: Extending the Class
Our Tabs class is looking pretty sweet. We can use it to create numerous
instances on a page or across a site. Initializing it on any given page is only
a line or two of code.
But wait a sec, we started this whole thing off with a tabbed area that
loaded the content via Ajax. This new class doesn’t do that. Let’s extend
our class to add Ajax back into the equation.
216
MooTools Essentials

Identifying What Needs to Change
To get started altering our foundation class, we need to consider what we
need to add or change. For starters, we’re going to load the content in via
Ajax, which means we need URLs for each tab. In our previous class
(AjaxTabs in Chapter 14), each tab was a link. We got the URL from the
link. That could work here, too, but maybe we want to make it optional to
pass in a set of links instead. So we know we need some way to specify in
the options what the links are.
What else? Well, maybe we want the option to cache the results. If the user
clicks a tab, and we fetch the info for that tab from the server, there’s no
need to fetch it again if the user revisits the tab. These two changes will
require new events and new options. First, let’s add the options for the
URLs and the caching.
var AjaxTabs = new Class({
//Extend Tabs; unlike Implement, which lets
//you implement any number of classes, Extends
//can only take a single Class
Extends: Tabs,
options: {
//By default, we'll cache the results
cache: true,
//This empty array is the default for the URLs
//If the array remains empty, we'll try and get
//the URL from the tab element and assume it has
//an href property
urls: []
}
});
We now have a class that extends our Tabs class that has a few new
options. Let’s put those to use. Both of these options are going to be used
when we load the information via Ajax. This means that our show method
needs some additional logic.

MooTools Essentials
217

fetchTabContent: function(index, url) {
//Get the tab:
var tab = this.tabs[index];
//Get the container we’re going to update:
var container = tab.retrieve('container');
//See if we've already got an instance
//of Request.HTML for this tab:
var request = tab.retrieve('tabAjax');
//If not, we’ll need to create one:
if (!request) {
request = new Request.HTML({
//Tell it to insert the HTML into our container
update: container,
url: url, //Using the URL we got earlier
onSuccess: function(){
//Show the container, and force it not to
//check for caching
this.show(index, true);
//On success the HTML is automatically
//injected into our container, so all
//that's left to do is set the loaded
//flag:
tab.store('loaded');
}.bind(this) //Don't forget to bind the "this"
});
tab.store('tabAjax', request);
}
request.send();
}
});
Now our class will attempt to get the URL for each tab and then get the
data from the server, update the container, and then show it. We reuse the
instances of Request.HTML so that we don’t create a race condition. We
set a flag to cache the results if our options tell us to do so.
We now have two classes—Tabs, which handles the basic functionality of
a tabbed layout, and AjaxTabs, which extends that class to add just the

MooTools Essentials
219

Ajax bit. If, in the future, we decided to add more functionality to our Tabs
class, our AjaxTabs class will automatically inherit that functionality.
Here’s what it would look like to instantiate our extension:
var myAjaxTabs = new AjaxTabs($$('div.container'),
$$('div.tab'), {
urls: ['/page1.html', '/page2.html',
'/page3.html', '/page4.html']
});
//Or, if our tabs are links
var myAjaxTabs = new AjaxTabs($$('div.container'),
$$('a.tab'));
Adding a Few More Options and Events
var AjaxTabs = new Class({
Extends: Tabs,
options: {
cache: true,
urls: [],
//Create the new option to be passed to Request
requestOptions: {}
},
show: function(index, force){
var tab = this.tabs[index];
var url = this.options.urls[index] ||
tab.get('href');
if (!url || force ||
(this.options.cache && tab.retrieve('loaded'))) {
this.parent(index);
} else {
this.fetchTabContent(index, url);
}
},
fetchTabContent: function(index, url) {
var tab = this.tabs[index];
var container = tab.retrieve('container');
var request = tab.retrieve('tabAjax');
220
MooTools Essentials

if (!request) {
//Here things get tricky; we need to merge the
//options with the data for this tab; we put the
//tab data last to make sure it overwrites
//anything in the options
request = new Request.HTML(
$merge(this.options.requestOptions, {
update: container,
url: url,
//Additionally, we need to allow for
//the options to specify their own
//onSuccess method, so we'll remove
//ours from the options and add our
//event to the instance
onSuccess: function(){
tab.store('loaded', true);
this.parent(index);
}.bind(this)
   })
//Here we attach our own onSuccess method. If
//there's an onSuccess method in the options,
//it'll fire before ours
  ).addEvent('onSuccess', function(){
tab.store('loaded', true);
this.show(index, true)
}.bind(this));
tab.store('tabAjax', request);
}
request.send();
}
});
This was a little tricky. We create an empty object in our options for the
options to be passed along to the Request.HTML instance, but we need to
specify the URL and the DOM element to update based on which tab got
clicked. We use $merge to combine the two, making sure our URL and
container are preserved by making them the second argument sent to

MooTools Essentials
  221

$merge. Additionally, since the options might include an onSuccess
method, we need to move our method out of the options so they don’t
collide. We do this by using the addEvent method to attach our event after
we create the instance. So long as we add this event before we send the
request, we won’t have a problem. You can have as many functions
attached to an event as you like.
Here’s what that might look like in use:
var myAjaxTabs = new AjaxTabs($$('div.container'),
$$('div.tab'), {
urls: ['/page1.html', '/page2.html',
'/page3.html', '/page4.html'],
requestOptions: {
//Stop requests if the user clicks another tab
//before the previous one loads:
link: 'cancel',
evalScripts: true,
onSuccess: function(response){
alert('Hey, ajax worked! Here\'s the response: '
+ response);
}
}
});
Review
We’ve now written two classes. The first one lets us manage tabs, and the
second one adds Ajax functionality. Now we can initialize our classes on
our pages with only a line or two of code. We can configure the behavior
and manage several different types of uses, all with the same code. Nice!
Here’s the code in its entirety without all the messy comments:
222
MooTools Essentials

show: function(index, force){
var tab = this.tabs[index];
var url = this.options.urls[index] ||
tab.get('href');
if (!url || force ||
(this.options.cache && tab.retrieve('loaded'))) {
this.parent(index);
} else {
this.fetchTabContent(index, url);
}
},
fetchTabContent: function(index, url) {
var tab = this.tabs[index];
var container = tab.retrieve('container');
var request = tab.retrieve('tabAjax');
if (!request) {
request = new Request.HTML(
$merge(this.options.requestOptions, {
update: container,
url: url
})
).addEvent('onSuccess', function(){
tab.store('loaded', true);
this.show(index, true)
}.bind(this));
tab.store('tabAjax', request);
}
request.send();
}
});

MooTools Essentials
225

Chapter 16: Where to Learn More
Once you have the hang of writing JavaScript with MooTools, and this
book doesn’t seem to have any more secrets for you to uncover, there’s still
a lot of resources you can turn to for improving your skills.
The first place to start is MooTools itself. Look inside the code and try and
pick apart some of its classes. The effects series of classes start with a very
abstract foundation class (Fx), which is extended to add layers that are
easier to worry with (Fx.Tween, Fx.Morph). Studying things like this will
not only help you understand MooTools more, but also see new ways of
doing things.

MooTools Essentials
227

There’s one last resource on MooTools that often escapes the notice of
many people, and that’s probably because it’s not well publicized.
MooTools has an IRC channel:
You’ll often find the principal developer (Valerio Proietti) hanging out
there, along with several members of the development team.
228
MooTools Essentials

Appendix: Core Concepts in JavaScript
There are a handful of important concepts that you need to be aware of
with JavaScript, and if you aren’t aware of them, stuff just won’t work.
DOCTYPE Matters
It’s important that you use a proper document type. I recommend XHTML
Strict, but others will work (XHTML Transitional, for example). Here’s an
example of a strict DOCTYPE:
There’s sample documentation online about document types and how they
work. I don’t spend much time thinking about the subject and just use Strict
all the time.
If you don’t specify a DOCTYPE or if you use one that isn’t XHTML,
you’ll get strange results when you try and use several of the classes and
effects in MooTools.
Type Coercion: “Falsy” and “Truthy” Values
JavaScript’s conditionals will do type coercion, and this is an important
thing to know about, because if you don’t, you can get into trouble. It’s not
a bad thing (if you ask me), so long as you know what to watch out for. In
fact, it’s quite useful for writing concise code.
What do I mean by type coercion? Consider this example:
var x = 0;
if (x) alert('x is truthy!');

MooTools Essentials
229

In the preceding code, the alert will never execute because JavaScript
interprets zeros as being “falsy.” The same is true for empty strings,
undefined, null, NaN (Not a Number), and, of course, false.
Further, try this code out in your browser (in the Firebug console for
example):
0 == "" //true!
false == 0 //true!
false == "" //true!
Note that this really only applies to items that are coerced. For example:
"3" == 3
"false" != false //Though "false" == true,
//and for that matter, so does "true"
Also note that if you are referring to objects in memory (arrays, objects,
i.e., {}, etc.) can be coerced as true, but never anything else. You don’t
have to work about "3,2,1" == [3,2,1] or anything.
Further, if you do the following:
{} == {}
[] == []
[1,2,3] == [1,2,3]
they are all false, because they are not the same object, despite the fact that
they are both arrays or objects with equal values.
You can force type coercion by using the ! and !! to produce Booleans:
var x = !!"foo"; //x is true
var x = !"foo"; //x is false
To avoid type coercion, you must use === and !== if you wish to be
explicit:
var x = 0;
if (!x) alert ('x is falsy!');
if (x !== false) alert('x is NOT *false*');
230
MooTools Essentials

Type coercion is not always a bad thing. In fact, it’s used throughout
MooTools, and there are even some methods that help you work with it
more explicitly. Here’s an example of how type coercion might be used:
var anchors = document.getElementsByTagName('a');
if (anchors.length) setup(anchors);
Here we save a few keystrokes (instead of writing if (anchors.length
> 0)), but sometimes what you need to evaluate could be null,
undefined, or an empty string, and writing a conditional to deal with all of
those possibilities is more than two or three keystrokes.
Functional Programming (a.k.a. Lambda)
JavaScript is one of the most popular functional programming languages,
but it’s not alone. To quote from the Wikipedia page on the subject:
Pure functional programming languages typically enforce referential transparency,
which is the notion that “equals can be substituted for equals”: if two expressions have
“equal” values (for some notion of equality), then one can be substituted for the other
in any larger expression without affecting the result of the computation.
Functional programming can be illustrated with the following examples:
function sum(x,y) {
return x+y;
}
//Passing the result of the sum function as an argument
alert(sum(1,2));
//Has the same result as storing that value in
//a variable:
var onePlusTwo = sum(1,2);
alert(onePlusTwo);
//But the same thing could be accomplished with
//an anonymous function:
alert(function(x,y){ return x+y; }(1,2));

MooTools Essentials
231

Here you can see how the result of all three alerts will be the same. The
first and third examples evaluate a function as an argument to another one,
passing the result as the argument.
This is also how a practice called chaining works. A function returns a
value that contains its own methods, which can be executed immediately:
['one','two','three'].concat(['four']).toString();
First, we have an array with three values, and we execute a method called
concat, which returns the array. When we execute toString, we are
executing it on the result returned from concat.
It’s very common practice to use these patterns in MooTools and
JavaScript in general, and understanding them will make it easier to
understand the examples in this book and the code you see in MooTools
and elsewhere.
Literals and Anonymous Functions
Two very common patterns that you’ll see in MooTools and other
JavaScript frameworks are the use of literal declarations and anonymous
functions.
Literal declarations are an alternative to declaring a value into a variable
namespace. This is often done when passing arguments to a function. If a
function accepts an array or an object, you can pass it one without
declaring it first:
function sumArrayValues(array){
var value = 0;
for (var i = 0; i < array.length; i++){
value += array[i];
}
return value;
};
var sum = sumArrayValues([0,1,1,3,5,8]); //sum is 18
232
MooTools Essentials

Here we’ve passed an array ([0,1,1,3,5,8]) to our function without
defining that array into a variable namespace. This pattern is often used for
numbers, strings, functions, arrays, and objects:
//An object literal:
armNinjas({
swords: 10,
stars: 99,
flyingGuillotines: 1
});
//An anonymous function:
setNinjaAttackMethod(function(weapons){
ninja.leftHand = weapons.sword;
ninja.righHand = weapons.star;
});
//Strings and numbers are much more familiar
//10 here a literal number; it isn't defined into
//a variable. Same goes for "poisoned":
giveNinjaStars(10, "poisoned");
“this” and Binding
JavaScript has a somewhat irregular scope schema that takes a little getting
used to. For starters, the only things that have scope are functions.
Conditional statements and iterations (if/else, try/catch, and for
loops, while, switch, etc.) don’t have scope; only functions do.
The other concept, which is a little hard to grok, is the this keyword. this
is a pointer to an object that represents the current scope. By default, this
is the window DOM object. When you declare a variable name or a
function in your code, you are creating a property of the window. Thus,
these are all the same thing:
var x = 10;
alert(window.x); //10
alert(x); //10
alert(this.x); //10

MooTools Essentials
233

Inside of a function you have a scope, but things can escape out of it. For
example:
function test(){
x = 10;
var y = 20;
};
test();
alert(window.x); //10
alert(window.y); //undefined
By declaring the variable y using the var prefix, we confine that variable to
the test function’s scope. When you declare a variable without the var
prefix, the JavaScript parser will attempt to find a reference to that variable
in the current scope, and, if it cannot find it, it will search the parent scope
and the parent’s parent until it reaches and searches the window scope. If it
finds the variable, it will change it; otherwise it will create that variable in
the global namespace (the window). This was intended to make JavaScript
easier for people who weren’t used to writing code; however, if you ask
me, it is just another example of the authors of the language trying to make
it more forgiving but instead making it more unclear, but I digress.
OK, so now you understand how functions have scope. The next thing that
you need to understand is that, in JavaScript, everything inherits from the
Object prototype (see “Prototypal Inheritance” later in this appendix). The
Object prototype has a few methods, none
So functions extend this prototype and add their own methods. Array does
the same, and so does String, Number, Element, and so on.
Because functions are objects, you can assign properties to them. For
example:
234
MooTools Essentials

constructor (with the new prefix), you get back an object that represents the
scope inside that function.
function whatsThis(){
alert(this);
};
whatsThis(); //Window
new whatsThis(); //Object - the object for
//this invocation of whatsThis
When you just call a function, the this is the scope from which you call it.
What this means is that it’s possible to instruct a function what the this
scope should be. By default, yes, it’s the window, but you can also tell a
function to use a different this. But why would you?
Turns out, there are a LOT of reasons. You’ll use this ability all the time.
Sometimes it’s kind of crazy how much you’ll want to use it, which is why
it’s crucial that you understand it well before you start really using
MooTools.
Because MooTools makes use of the functional programming concepts
outlined in previously in this appendix, you’ll pass functions as arguments
to other functions. Let’s take the Array.each extension that MooTools
adds to the Array prototype. Array.each takes two arguments: a function
and an object to be used for binding (the latter is optional). Here’s an
example of it in action:
['blue','green','yellow'].each(function(value, index){
alert('item ' + index + ' is ' + value);
//Alerts:
// "item 0 is 'blue'"
// "item 1 is 'green'"
// "item 2 is 'yellow'"
if (index == this.length-1) this[index] = 'orange';
//Changes the last item in the array to 'orange'
});
236
MooTools Essentials

In this example, we pass an anonymous function to the each method. The
each method loops through the items in the array and invokes the function.
Because the method invoking that function is a property of the array, the
this keyword points to the array. Our function can reference the array
only by using the this keyword (how else could it?).
Consider this example:
var example = {
say: function(msg) {alert(msg); },
count: function(){
[1,2,3].each(function(number) {
this.say(number);
});
}
};
Now wait a second. Here we’re trying to reference the say method, and we
could because inside the count method the this keyword points to the
example object. But we’ve already seen that the function that we pass to
Array.each has its this keyword mapped to the array. We need to
instruct this function that its this is NOT the array—it’s the example
object.
And that’s what binding does. It lets us tell a function what its this is:
var example = {
say: function(msg) { alert(msg); },
count: function(){
[1,2,3].each(function(number) {
this.say(number);
}, this); //Here's the important part!
}
};
By passing along the this context here, we now can reference
example.say inside our each function.

MooTools Essentials
237

I said earlier that this gets used a LOT in MooTools, and it does. It’s a
core concept of JavaScript, so it’s not just MooTools that makes use of it.
There are countless examples of where it’s used, but principally it’s used
where functions are passed as arguments. Other cases exist, but typically
you’ll apply it to anonymous functions.
Some methods (like each) allow you to pass the bound object as an
argument, but not always. When this isn’t an option, you’ll have to use the
bind method that’s added to the native function object by MooTools.
Here’s an example of that in action:
//Imagine this code is inside of a broader scope, as
//with the previous example
$('myElement').addEvent('click', function(){
this.say('clicked!');
}.bind(this)); //Here's the important bit
When you start digging into Chapters 13 and on where we start actually
looking at MooTools in action, you’ll see lots of references to binding, and
you’ll start to get an idea of all the places where this practice comes into
play. Simply put, binding and the this keyword are two of the most
important concepts to grasp in modern JavaScript-ing.
Closures
One concept in JavaScript that is quite powerful is closure. A closure is a
function declared or evaluated in a scope with bound variables, i.e.,
variables declared in the same scope as a function are accessible by that
function. Another way to put this is that the scope of an inner function
continues to exist even after the parent function has returned.
Let’s consider this function, which will change the color of a box from
white to black:
238
MooTools Essentials

Array called sum that would add up all the values in an array that were
numbers, you could:
Array.prototype.sum = function(){
var result = 0;
for (var i = 0; i < this.length; i++) {
var value = parseInt(this[i]);
if (!isNaN(value)) result += value;
}
return result;
}
alert([1,2,3].sum()); //Alerts "6"
All objects in JavaScript begin with the native Object prototype.
Functions, Arrays, Numbers, Strings, and so forth all inherit from
Object, which is one of the reasons why altering the Object prototype is
considered forbidden.
What this means is that, say, Functions can have properties just like
Objects can. So can Arrays. In the example, Array.sum is just a property
of the Array prototype. You could also define that method for a specific
array rather than all of them. For example:
var numbers = [1,2,3];
numbers.sum = function(){
var result = 0;
for (var i = 0; i < this.length; i++) {
var value = parseInt(this[i]);
if (!isNaN(value)) result += value;
}
return result;
}
alert(numbers.sum()); //Alerts "6"
The result here is that we’ve added a property to the array that isn’t a value
of the array’s contents (1, 2, 3). Similarly, we can define properties of a
function:
240
MooTools Essentials

Don’t worry about how the inheritance gets applied, that’s what MooTools
helps you do (see the discussion on classes in Chapter 7).
If our code references redNinja.isAlive, the Ninja object doesn’t have
that property, so Human is inspected. Human doesn’t have that property
either, so it goes up the chain to Animal, which does have that property.
This is not to say that all instances of Human or Ninja share the same value
for that property. It’s more like saying that the default value for all Humans
and Ninjas is that their property isAlive is true.
If we were to execute the code:
redNinja.isAlive = false;
in addition to being sad because our ninja has died, what we would observe
is that now redNinja has its own property for isAlive. The Animal
prototype still has an isAlive property with the value of true, but when
we inspect redNinja.isAlive, we don’t go up the chain to the prototype
because redNinja has that property.
One of the little gotchas that can occur here is that it is possible to delete a
property from an object. If that property is defined for an object’s
prototype, deleting the value from the object does not necessarily mean that
the value is now undefined.
Consider this:
//Continuing from the preceding code
//where the chain is Animal > Human > Ninja
//and Animal.isAlive defaults to true
redNinja.isAlive = false;
if(!redNinja.isAlive)
alert("Oh what grief, our ninja is dead!");
delete redNinja.isAlive;
if(redNinja.isAlive) alert("Oh happy day! Our ninja is
alive again!");
242
MooTools Essentials

By deleting the isAlive property from our Ninja instance, we revert back
to the value contained in Animal.
This inheritance model—the prototypal inheritance model—is different
from Classical inheritance and can take some getting used to. Thankfully,
MooTools has tools to help us manage these relationships.
Unobtrusive JavaScripting
It’s good practice to have as little JavaScript in your actual document as
possible. Opinions differ on whether JavaScript is best served externally or
as a long string at the top of the document (for speed purposes), but it’s
now common practice to avoid having JavaScript mixed in with your
HTML.
Even if you decide for your own design purposes to deliver JavaScript with
the page (and sometimes it makes sense to do this), you should separate the
JavaScript from the HTML. Not only does this make it easier to manage
your code base, but it also makes your layouts more reusable.
So, for example, compare the following two examples:
While both examples work just fine, the latter example is much easier to
find and understand. When you pepper your HTML with function calls, it’s
difficult to maintain, especially when things get complicated (and when
you’re using Ajax to replace content and effects to fade stuff in and out, it

MooTools Essentials
243

gets even more complicated!). Additionally, if you deliver your JavaScript
externally, your HTML documents will be clean, vanilla HTML and are
more likely to degrade gracefully when things go wrong.
Additionally, by using unobtrusive methods, you can add more than one
event to an element, or remove an event at a later time.
Note
The JavaScript compiler in the browser has an odd feature:
when the compiler encounters an error, it attempts to replace the nearby
end of line with a semicolon and parse again. This was designed to make
JavaScript “easier” for an audience that may not be used to strict standards
in the things they were normally writing (in theory, HTML). The result is
that if you have code that does not have a semicolon at the end of every
declaration, the compiler will insert them for you. However, when
compressing JavaScript, all line breaks are removed, which means that if
you have any lines that are lacking semicolons, your code will break. Always
put semicolons at the end of any of your declarations. Example:
var ninja;
var ninja.visible = false;
var assassinate = function(ninja, target){
ninja.kill(target);
};
ninja.weapons = ['star','sword','surprise'];
//You do NOT have to put semicolons at the
//end of statements no semicolon necessary after
//if/else, for, while, etc.
if (target.isAlive){ ninja.kill(target);}
for(var i = 0; i < targets.length; i++){
ninja.kill(target[i]);
}

244
MooTools Essentials

DomReady
Unobtrusive JavaScripting has a downside, though. In order to add
functionality to the document (more specifically the Document Object
Model, or DOM), you have to wait for the DOM to load. You can only
collect elements from the DOM if they are in memory, which means your
code can’t safely run until the document is loaded.
Traditionally, the window.onload event was used for executing such code,
but the onload event fires only after all the HTML has loaded and all the
assets in it (the images, CSS, JavaScript, etc.). By the time every image and
advertisement has loaded, the user can see the page and in some cases has
already clicked something on the page, and it’s too late to execute your
code.
This is where the DomReady event comes into play. This event is added to
the DOM by MooTools and fires as soon as the HTML is in memory but
doesn’t wait for any assets to load. By attaching your DOM scripting code
to DomReady, you can usually execute your code before the layout is drawn
by the browser.
<script>
//Execute my method attack when the DOM is loaded
window.addEvent('domready', ninjas.attack);
</script>
You can find more information on how addEvent and DomReady work in
Chapters 5 and 6, respectively.
Namespacing
When writing implementation code—code that isn’t meant to be reused,
but instead sets up all the actions and functionality for a page (for example,
turn these images into a slide show, expose this content when the user
clicks that link, etc.)—a common practice is to make all the variables and
functions members of an object.

MooTools Essentials
245

This practice pays several dividends. Most notably, you don’t have to
worry about another bit of code overwriting your function and variable
names. So long as the namespace you choose is unique, any property you
add to it is safe. Additionally, it helps keep your code organized and tidy.
<script>
var ninjas = {
function: attack(){
for(var i = 0; i < ninjas.targets.length; i++){
ninjas.kill(ninjas.targets[i]);
}
},
kill: function(target){
target.isAlive = false;
},
targets: ['fred', 'bill', 'white ninja']
};
ninjas.attack(); //!!!
</script>
By assigning functions and variables as members of a single namespace, it
doesn’t matter the order that they are declared; you can reference members
that are not yet defined, and you don’t have to worry about someone using
the function name kill because yours is in the ninjas namespace.
246
MooTools Essentials

Document Outline

Prelims
Contents
Preface
- Acknowledgments
- A Note on the Code Formatting in This Book
Introduction
- JavaScript Frameworks
- Why You Should Use a JavaScript Framework
- About This Book
  - Who This Book Is For
  - What You Need to Know
- Summary
Chapter 1: Getting Started with MooTools
- Downloading MooTools
  - Downloading MooTools Official Plug-Ins
  - Core Builder
  - Making Use of MooTools� Modular Design
  - Compatibility
  - Compression Options
- Adding MooTools to Your Page(s)
- Coding for Reuse
- Compression
  - Using the YUI Compressor
Chapter 2: Reviewing MooTools
- MooTools File Structure
- Manifest of MooTools Scripts
  - The MooTools Core
  - The MooTools Plug-Ins: fiMoref
Chapter 3: Shortcuts and Helpful Functions
- Determining the Type of an Object:
  - :: Core/Core.js
- Checking Whether Values Are Defined: $defined, $chk, and $pick
  - :: Core/Core.js
- Working with Objects:
- ,
- , and
  - :: Core/Core.js
- Iterable Helpers and Shortcuts:
- ,
- and
  - :: Core/Core.js
- Other Shortcuts:
- ,
  - :: Core/Core.js
- Browser: Information About the Client
Chapter 4: Native Objects
- Native.implement
- Arrays
  - Array Methods
  - :: Iteration Methods
  - Array.each
  - Anonymous Methods vs. Named Functions
  - Other Iteration Methods
  - :: Introspection Methods
  - :: Manipulation Methods
- Objects (a.k.a.
- )
  - Hash
  - $H
  - Hash Methods
  - :: Iteration Methods
  - Hash.each
  - Other Iteration Methods
  - :: Introspection Methods
  - :: Manipulation Methods
- Functions
  - Function Methods Generate Copies
  - Numbers
  - Strings
  - Events
  - Event Methods
  - Event Properties
Chapter 5: Elements
- Creating and Cloning Elements
- Collecting Elements from the DOM
  - :: Element/Element.js
  - Using
  - to Ensure You Have an Initialized Element
  - :: Element/Element.js
- Element Methods and Collections
  - :: Element/Element.js
- Element Methods for Collecting Children, Siblings, and Parents
- Setting, Getting, and Erasing Properties of Elements
  - Element.set
  - Element.get
  - Element.erase
  - Custom Getters and Setters and Erasers
- Element Injection and Removal
- Element (CSS) Classes
- Element Storage
  - What�s New in 1.2: Element Storage
- The Elements Object
  - Elements Methods
  - Elements.filter
- Other Element Methods in
- Element.Event.js
  - Adding and Removing Element Events
Chapter 6: Utilities
- Selectors
  - Complex CSS3 Expressions
- DomReady
  - The DomReady Custom Event
- JSON
  - MooTools and JSON
  - JSON.encode
  - JSON.decode
- Cookie
  - Cookie.write
  - Cookie.read
  - Cookie.dispose
- Swiff
  - Swiff Constructor
  - Swiff.replaces, Swiff.inject
  - Swiff.remote
Chapter 7: Classes and Inheritance
- Using the Class Constructor
- Initialization
- Inheritance
- Implement vs. Extend
- Extending Classes
- Extending Classes into Themselves
- Implementing Classes
- Implementing Classes into Other Classes
Chapter 8: Getting Started with Classes
- Class.Extras
  - The Options Class
  - The Events Class
  - The Chain Class
Chapter 9: Fx
- Fx and Fx.CSS
  - Fx Options
  - Fx Events
  - Fx.start
  - Fx.set
  - Fx.cancel, Fx.pause, Fx.resume
- Fx.Tween
  - Element.tween
- Fx.Morph
  - Element.morph
  - Element.set/get with Fx.Morph
  - Using CSS Selectors with Fx.Morph
- Fx.Transitions
  - The Transitions
  - Specifying a Transition for an Effect
  - Creating Your Own Transition
- The Rest of Fx.*
Chapter 10: Request
- Request
  - Request Options
  - Request.send
  - Request: .get, .post, .put, .delete
  - Request.cancel
  - Element.send
- Request.HTML
  - Element.load
- Request.JSON
Chapter 11: Plug-Ins
- A More General Overview
- Assets
  - Assets.javascript
  - Assets.css
  - Assets.image
  - Assets.images
- Accordion
- Fx.Slide
- Fx.Scroll
- Fx.Elements
- Drag
  - Element.makeResizeable
- Drag.Move
  - Element.makeDraggable
- Color
- Group
- Hash.Cookie
- Sortables
- Slider
- Scroller
- Tips
Chapter 12: Third-Party Plug-Ins
- The CNET Clientside Libraries
  - dbug
  - Browser.Extras
  - Native Extensions
  - Element Extensions
  - Effects Extensions
  - Request
  - UI
  - Layout
  - Forms
- Other Third-Party Scripts
  - Autocompleter, FancyUpload, ReMooz, SqueezeBox, Roar
  - Slimbox
  - . . . And More
Chapter 13: Real-World Examples
- A Simple Page
- Dissecting the Example
- Summary
Chapter 14: Writing a Tab Class
- Step 1: Creating an Empty Class
- Step 2: Defining Arguments
- Step 3: Defining Methods
- Instantiating Our Class
- Review
Chapter 15: Writing Flexible Classes
- Step 1: Creating a Foundation Class
  - A Note on Using Methods
- Step 2: Adding Options
- Step 3: Adding Events
  - Making Good Use of Events
  - Adding Events After Invokation
  - You Don�t Have to Declare Events in the Options Object
- Step 4: Extending the Class
  - Identifying What Needs to Change
  - Adding a Few More Options and Events
- Review
Chapter 16: Where to Learn More
Appendix: Core Concepts in JavaScript
- DOCTYPE Matters
- Type Coercion: fiFalsyfl d fiTruthyfl Vaes
- Functional Programming (a.k.a. Lambda)
- Literals and Anonymous Functions
- fithisfl d Binding
  - Binding
- Closures
- Prototypal Inheritance
- The Inheritance Chain
  - Unobtrusive JavaScripting
  - DomReady
  - Namespacing
Related Titles
Copyright

А также другие работы, которые могут Вас заинтересовать
15279.	Лабораторная работа	Команди і директиви мови Асемблер	122.5 KB
	Лабораторна робота № 4 Тема: Команди і директиви мови Асемблер. Мета роботи: Набути навичок застосування асемблерних команд передачі інформації. Засвоїти способи адресування операндів вказаних груп команд та алгоритми їх виконання.
15280.	Лабораторная работа	Застосування асемблерних команд з реалізації арифметичних, логічних операцій і операцій зсуву	156 KB
	Лабораторна робота № 5 Тема: Команди і директиви мови Асемблер. Мета роботи: Набути навичок застосування асемблерних команд з реалізації арифметичних логічних операцій і операцій зсуву. Засвоїти способи адресування операндів вказаних гру
15281.	Лабораторная работа	Застосування асемблерних команд передачі управління. Алгоритми їх виконання	110.5 KB
	Лабораторна робота № 6 Тема: Команди і директиви мови Асемблер. Мета роботи: Набути навичок застосування асемблерних команд передачі управління. Засвоїти алгоритми їх виконання. Короткі теорет
15282.	Лабораторная работа	Алгоритми функціонування ланцюгових команд та способи формування адреси операнда-джерела і адреси операнда-призначення	145.5 KB
	Лабораторна робота № 7 8 Тема: Команди і директиви мови Асемблер. Мета роботи: Засвоїти алгоритми функціонування ланцюгових команд та способи формування адреси операндаджерела і адреси операндапризначення за якими розташовуються ланцюго
15283.	Лабораторная работа	Технологія та прийоми програмування мовою Асемблер	142 KB
	Лабораторна робота № 9 Тема: Технологія та прийоми програмування мовою Асемблер. Мета роботи: Набути навичок роботи з масивами при програмуванні мовою Асемблера. Навчитися описувати одновимірні масиви в програмі; ініціювати масив; орган...
15284.	Лабораторная работа	Налагодження програми мовою Асемблер з оброблення двовимірних масивів	149 KB
	Налагодження програми мовою Асемблер з оброблення двовимірних масивів Лабораторна робота № 10 Тема: Технологія та прийоми програмування мовою Асемблер. Мета роботи: Набути навичок роботи з масивами при програмуванні мовою Асемблера.
15285.	Лабораторная работа	Налагодження програми мовою Асемблер з використанням циклів та розгалужень	102.5 KB
	Налагодження програми мовою Асемблер з використанням циклів та розгалужень Тема: Технологія та прийоми програмування мовою Асемблер. Мета роботи: набути навичок з реалізації задач мовою Асемблер що містять цикли та розгалуження. Ко...
15286.	Лабораторная работа	Налагодження програми мовою Асемблер з використанням арифметичних операцій	76.5 KB
	Налагодження програми мовою Асемблер з використанням арифметичних операцій Лабораторна робота № 13 Тема: Технологія та прийоми програмування мовою асемблера. Мета роботи: Набути навичок з реалізації математичних задач мовою асемблера....
15287.	Лабораторная работа	Налагодження програми мовою Асемблер з використанням логічних операцій	76 KB
	Налагодження програми мовою Асемблер з використанням логічних операцій Лабораторна робота № 14 Тема: Технологія та прийоми програмування мовою Асемблера. Мета роботи: Набути навичок застосування логічних команд при програмуванні мов...

Document Outline

А также другие работы, которые могут Вас заинтересовать