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50 minute talk on Ajax and JavaScript libraries, presented at Web 2.0 Expo Berlin on 7th November 2007.
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Simon Willison - http://simonwillison.net/Web 2.0 Expo Berlin
7th November 2007
librarieswork for you
This talk
• JavaScript libraries!
• What they are
• Why they exist
• What they can do for you
• How to pick one
JavaScript libraries
• ajaxpatterns.org lists over 40 general purpose JavaScript libraries
• ... and that’s not including the many libraries tied to a specific server-side language
• Why are there so many of them?
“The bad news: JavaScript is broken.
The good news:It can be fixed with more JavaScript!”
Geek folk saying
• Inconsistent event model (thanks, IE)
• Memory management (thanks, IE)
• The DOM is a horrible API!
• JavaScript-the-language has quite a few warts
• But it’s powerful enough to let you fix them
• Browser Ajax is far too verbose
• Positioning and co-ordinates
• Drag and drop and Animation are really hard
var xhr;if (window.XMLHttpRequest) { xhr = new XMLHttpRequest();} else if (window.ActiveXObject) { try { xhr = new ActiveXObject('Microsoft.XMLHTTP'); } catch (e) {}}xhr.onreadystatechange = function() { if (xhr.readyState == 4) { if (xhr.status == 200) { alert(xhr.responseText); } else { alert('Error code ' + xhr.status); } }}
• Prototype (and Scriptaculous)
• The Yahoo! User Interface Library - YUI
• jQuery
• The Dojo Toolkit
Narrowing them down...
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 Scriptaculous
• Prototype focuses on basic browser compatibility and JavaScript language enhancement
• It tries to make JavaScript more like Ruby
• Extends most of JavaScript’s built-in objects with new functionality
• Scriptaculous adds fancy effects, basic widgets and drag and drop
• $, $$, $F, $A, $H
• var Animal = Class.create(...)
• new Ajax.Request(url[, options])
• Event.observe(el, 'click', function() { ... })
• "foo-bar".camelize() -> "fooBar"
$$('#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
Script.aculo.us
The Yahoo UI Library
• 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'); 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);});
$E = YAHOO.util.Event;$D = YAHOO.util.Dom;
$E.on(window, 'load', function() { var div = $D.get('messages'); ...});
Common YUI idiom
jQuery
• Simple philosophy: find some nodes, then do something to them
• Minimal impact on your global namespace - it adds two global symbols: jQuery and $, and $ can be easily reverted
• API designed around “chaining” - other libraries are now emulating this
• Outstanding node selection, based on CSS 3 and custom extensions
• Small core library with a smart plugin mechanism
jQuery(window).ready(function() { jQuery("div.hideable"). css('cursor', 'pointer'). append('<p>Click to hide</p>'). click(function() { jQuery(this).hide("slow"); return false; });});
$(function() { $("div.hideable"). css('cursor', 'pointer'). append('<p>Click to hide</p>'). click(function() { $(this).hide("slow"); return false; });});
The Dojo Toolkit
• The oldest of the current popular libraries, pre-dating even the term “Ajax”
• Incredible amounts of functionality
• Used to suffer from a tough learning curve, but the 1.0 release greatly simplifies things
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
Dojo 0.4
Dojo 1.0
dojo
dijitdojox
• dojo
• Core library, similar to jQuery / Prototype
• Dynamic code loading and dependency management
• dijit
• Advanced widget system
• dojox
• Dojo eXperimental - crazy voodoo magic
Dojo components
dijit
<div dojoType="dijit.layout.TabContainer" sizeShare="40"><div id="tab1" dojoType="dijit.layout.ContentPane" title="Form Feel"> <h2>Various Form Elements:</h2> <form name="dijitFormTest"><p><input type="checkBox" dojoType="dijit.form.CheckBox" checked="checked">Standard Dijit CheckBox<br><input type="checkBox" dojoType="dijit.form.CheckBox" disabled="disabled">Disabled Dijit<br><input type="checkBox" dojoType="dijit.form.CheckBox" disabled="disabled" checked="checked">Checked and Disabled Dijit</p>...
dojox
• Graphics (cross-browser drawing API)
• Offline storage
• Cryptography
• Templating
• Data grids and more
• “The future of the browser today”
Honourable mentions
Ext JS
The Google Web Toolkit
What are the interesting ideas?
Interaction Design Patterns
Smart node selection
• Any JavaScript that modifies the page inevitably starts out by selecting some existing nodes
• jQuery is based entirely around node selection
• Prototype and Dojo also have node selection APIs
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
So how do you pick one?
• It depends on what you are trying to build
So how do you pick one?
My library selection criteria
• Enables unobtrusive JavaScript
• Plays well with other code
• Smart use of namespacing
• Global variable impact kept to a minimum
• Tie breaker: the less code I have to write the better!
• I’m currently using and recommending jQuery for most situations
• But... there’s cut-throat competition between the various libraries at the moment
• This is one of the reasons I care about interoperability - commit to a single library and you might lose out when one of the others jumps ahead of it
The law of leaky abstractions
The more you rely on abstractions, the worse off you’ll
be when one of them leaks
http://www.joelonsoftware.com/articles/LeakyAbstractions.html
My interpretation:
Thank you!