JavaScript Libraries:The Big Picture
Simon WillisonXTech, 16th May 2007
• What problems do libraries solve?
• An overview of the Big Four
• ... what are the interesting ideas?
Personal bias
• I like JavaScript-the-language
• So I won't be talking about frameworks that generate JavaScript code for you
Douglas Crockford
“ The Web is the most hostile software engineering environment imaginable.”
The legacy of the browser wars
• The DOM API kind of sucks
• Event handling is frequently broken
• Ajax is inconsistent
• You have to roll your own animation
• Drag and drop is tricky
• Co-ordinates are surprisingly hard
• Internet Explorer leaks memory like a sieve
The Event model// Internet Explorer
element.attachEvent('click',
function() {
alert(window.event);
}
)
// Everyone else
element.addEventListener('click',
function(ev) { alert(ev) }, false
);
“The bad news: JavaScript is broken.
The good news:It can be fixed with more JavaScript!”
Geek folk saying
The big four
• The Dojo Toolkit
• The Yahoo! User Interface Library
• Prototype (and Script.aculo.us)
• jQuery
The Dojo Toolkit
• Founded in 2004
• Originally unified from a bunch of older frameworks
• Initial aim was to show that JavaScript / DHTML should be taken seriously
• Enormous amount of smart technology
http://www.flickr.com/photos/aprillynn77/8818200/
dojo.collections
dojo.crypto
dojo.date
dojo.dnd
dojo.dom
dojo.event
dojo.io
dojo.lang
dojo.lfx
dojo.logging
dojo.math
dojo.reflect
dojo.rpc
dojo.storage
dojo.string
dojo.style
dojo.undo
dojo.uri
dojo.widget
dojo.xml
dijit• The Dojo widget system
• Create widgets programmatically, or use declarative markup
<div dojoType="dijit.TitlePane"
label="Terms and Conditions"
width="200">
Text...
</div>
The future today
• Cross browser 2D drawing APIs
• dojo.storage - store data offline
• dojo.undo.browser - history management
• The Dojo Offline Toolkit
The Yahoo! User Interface Library
YUI
• Created at Yahoo!, BSD licensed
• Designed for both creating new applications and integration with legacy code
• Focused on browser issues; almost no functionality relating to JS language itself
• Extensively tested and documented
dom event connection
animation dragdrop
utilities
controls
autocomplete calendar
menu slider treeview
container
YAHOO.util.Event.on(window, 'load', function() { var div = YAHOO.util.Dom.get('messages'); if (!div) { return; } setTimeout(function() { var anim = new YAHOO.util.Anim(div, { height: {to: 0}, opacity: {to: 0} }, 0.4); anim.animate(); anim.onComplete.subscribe(function() { div.parentNode.removeChild(div); }); }, 2000);});
Download API Docs Tips and Tutorials Blog Discuss Contribute
Prototype is a JavaScript Framework that aims toease development of dynamic web applications.
Featuring a unique, easy-to-use toolkit for class-driven
development and the nicest Ajax library around, Prototype
is quickly becoming the codebase of choice for web
application developers everywhere.
Prototype and script.aculo.us: The "Bungee
book" has landed!
Core team member Christophe
Porteneuve has been hard at work
for the past few months tracking
and documenting Prototype for his
new book Prototype and
script.aculo.us, which is now
available as a Beta Book from the
Pragmatic Programmers (and is
scheduled to ship later this year).
Read more !
DownloadGet the latest version—1.5.1
LearnOnline documentation and resources.
DiscussMailing list and IRC
ContributeSubmit patches and report bugs.
Who's using Prototype?
Meet the developers
© 2006-2007 Prototype Core Team | Licenses: MIT (source code) and CC BY-SA (documentation).
Prototype and Script.aculo.us
• Integrated with Ruby on Rails, but can be used separately as well
• Small, readable codebase - Prototype is just 3,000 lines
• Makes JavaScript behave more like Ruby
• This is a dual-edged sword
$$('#bmarks li').each(function(li){ Event.observe(li, 'click', function(e) { this.style.backgroundColor = 'yellow'; }.bindAsEventListener(li));});
• Wizzy extension for Prototype
• Huge collection of packaged effects
• AutoComplete, Slider, InPlaceEditor controls
• Drag and drop
• Easier DOM building
Script.aculo.us
jQuery
$(document).ready(function(){ $("a").addClass('hidden').click( function() { $(this).hide("slow"); return false; }); );});
It’s not a gimmick!
• API designed around “chaining”
• Built in support for onContentLoaded
• Outstanding node selection
• CSS 3, XPath and custom extensions
• Small core library, smart plugin mechanism
• visualjquery.com/ offers the best docs
!?
Playing well with others
“Namespaces are one honking great idea -- let's
do more of those!”
Tim Peters, “The Zen of Python”python -c "import this"
Prototype
var moo = $('moo');['foo', 'bar'].each(function(id) { // ...});"This is a string".dasherize()Object.toJSON({foo: 'bar'}
YUI
YAHOO.util.Event.on( YAHOO.util.Dom.get('foo'), 'click', function(ev) { YAHOO.util.Event.stopEvent(ev); // ... });
YUI idiomvar $E = YAHOO.util.Event;var $D = YAHOO.util.Dom;$E.on( $D.get('foo'), 'click', function(ev) { $E.stopEvent(ev); // ... });
jQuery
• Everything it does is encapsulated in the jQuery function / object
• $(...) is just a shortcut for jQuery(...)
• If it exists, the original $ function is stashed away in jQuery._$
• You can restore it with jQuery.noConflict()
jQuery.noConflict()<script src="prototype.js"></script><script src="jquery.js"></script><script>jQuery.noConflict();jQuery(function($) { $('div.panel').hide(); // ...});</script>
Progressive enhancement
http://www.neighbourhoodfixit.com/
Some neat ideas
Interaction Design Patterns
Smart node selection
• Progressive enhancement inevitably starts out by selecting existing nodes
• jQuery is based entirely around node selection
• Prototype has node selection as a key API
• YUI and Dojo just have getElementsByClassName
• YUI-ext offers smarter selections for YUI
Smarter Ajax
• Prototype makes it easy to set a callback for when ANY Ajax request completes... useful for loading status icons
• Ajax.Updater can extract and execute <script> blocks in HTML fragments
• Great for unobtrusively enhancing elements that have just been added to the page
Self-adjusting animations
• You can roll your own animations in JavaScript using setTimeout and setInterval...
• ... but the time taken for a animation will vary depending on browser performance
• Smarter animations adjust their framerate to compensate for browser performance
• All four libraries do this
DSLs for animation
var anim = new YAHOO.util.Anim('el', { opacity: {to: 0.5}, height: {to: 0}, fontSize: { from: 100, to: 50, unit: '%' }}, 1);anim.animate();
XPath optimisations
• Mozilla and Opera offer fast XPath lookups through document.evaluate(...)
• Dojo can use this for getElementsByClass()
• Prototype redefines getElementsBySelector to use XPath
Minification• All four libraries ship in both uncompressed
and compressed formats
• YUI uses minification: whitespace and comments are stripped
• The Dojo build system uses “ShrinkSafe”, which compresses JavaScript using the Rhino parser
• jQuery uses Dean Edwards’ Packer, with base62 encoding
Hosting on a CDN
http://yui.yahooapis.com/2.2.2/build/reset/reset-min.css
http://yui.yahooapis.com/2.2.2/build/dom/dom-min.js
...
http://o.aolcdn.com/iamalpha/.resource/jssdk/dojo-0.4.1/dojo.js
• JavaScript is cached before the user even visits your site
The law of leaky abstractions
You need to understand what your library is doing for you
Thank you
http://www.flickr.com/photos/klara/94704029/
http://www.flickr.com/photos/petele/407151800/
http://www.flickr.com/photos/adactio/464449077/
http://www.flickr.com/photos/thepartycow/62830567/
http://www.flickr.com/photos/lunchtimemama/97685471/