How to make Ajax Libraries work for you

How to make libraries work for you Simon Willison - http://simonwillison.net/ Web 2.0 Expo Berlin 7th November 2007

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); } } }

Narrowing them down... • Prototype (and Scriptaculous) • The Yahoo! User Interface Library - YUI • jQuery • The Dojo Toolkit

Download Get the latest version—1.5.1 Learn Prototype is a JavaScript Framework that aims to Online documentation and resources. ease development of dynamic web applications. Featuring a unique, easy-to-use toolkit for class-driven Discuss development and the nicest Ajax library around, Prototype Mailing list and IRC is quickly becoming the codebase of choice for web application developers everywhere. Contribute Submit patches and report bugs. Prototype and Scriptaculous Prototype and script.aculo.us: The quot;Bungee bookquot; has landed! Core team member Christophe Who's using Prototype? Meet the developers Porteneuve has been hard at work for the past few months tracking

• 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() { ... }) • quot;foo-barquot;.camelize() -> quot;fooBarquot;

$$('#bmarks li').each(function(li){ Event.observe(li, 'click', function(e) { this.style.backgroundColor = 'yellow'; }.bindAsEventListener(li)); });

Script.aculo.us • Wizzy extension for Prototype • Huge collection of packaged effects • AutoComplete, Slider, InPlaceEditor controls • Drag and drop

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

controls autocomplete calendar container menu slider treeview animation dragdrop dom event connection utilities

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); });

Common YUI idiom $E = YAHOO.util.Event; $D = YAHOO.util.Dom; $E.on(window, 'load', function() { var div = $D.get('messages'); ... });

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(quot;div.hideablequot;). css('cursor', 'pointer'). append('<p>Click to hide</p>'). click(function() { jQuery(this).hide(quot;slowquot;); return false; }); });

$(function() { $(quot;div.hideablequot;). css('cursor', 'pointer'). append('<p>Click to hide</p>'). click(function() { $(this).hide(quot;slowquot;); 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

dojo.collections dojo.math dojo.crypto dojo.reﬂect dojo.date dojo.rpc dojo.dnd dojo.storage dojo.dom dojo.string dojo.event Dojo 0.4 dojo.style dojo.io dojo.undo dojo.lang dojo.uri dojo.lfx dojo.widget dojo.logging dojo.xml http://www.ﬂickr.com/photos/aprillynn77/8818200/

dojo Dojo 1.0 dojox dijit

Dojo components • dojo • Core library, similar to jQuery / Prototype • Dynamic code loading and dependency management • dijit • Advanced widget system • dojox • Dojo eXperimental - crazy voodoo magic

<div dojoType=quot;dijit.layout.TabContainerquot; sizeShare=quot;40quot;> <div id=quot;tab1quot; dojoType=quot;dijit.layout.ContentPanequot; title=quot;Form Feelquot;> <h2>Various Form Elements:</h2> <form name=quot;dijitFormTestquot;> <p><input type=quot;checkBoxquot; dojoType=quot;dijit.form.CheckBoxquot; checked=quot;checkedquot;> Standard Dijit CheckBox <br><input type=quot;checkBoxquot; dojoType=quot;dijit.form.CheckBoxquot; disabled=quot;disabledquot;> Disabled Dijit <br> <input type=quot;checkBoxquot; dojoType=quot;dijit.form.CheckBoxquot; disabled=quot;disabledquot; checked=quot;checkedquot;> Checked and Disabled Dijit </p> ...

• 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?

So how do you pick one? • It depends on what you are trying to build

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

http://www.joelonsoftware.com/articles/LeakyAbstractions.html My interpretation: The more you rely on abstractions, the worse off you’ll be when one of them leaks

Thank you!

http://szklanowski.blogspot.com	147
http://lanyrd.com	35
http://www.slideshare.net	4
http://szklanowski.blogspot.ch	3
http://egox.tumblr.com	2
http://www.webgox.com	2
http://szklanowski.blogspot.co.uk	1
http://szklanowski.blogspot.ca	1

How to make Ajax Libraries work for you

by Simon Willison

Accessibility

Categories

Upload Details

Usage Rights

8 Embeds 195

Statistics

How to make Ajax Libraries work for you Presentation Transcript