jQuery Tool Objects - Speaker Deck

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jQuery Tool Objects othree@COSCUP

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Tools • Queue • Deferred • Callbacks

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queue http://www.ﬂickr.com/photos/hktang/4243300265/

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Timer • setTimeout • setInterval

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http://ejohn.org/blog/how-javascript-timers-work/

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Timer Issues • Timer not reliable • Race Condition between intervals

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Ideal setTimeout left +=10 left +=10 left +=10 left +=10 left +=10 10ms 20ms 30ms 40ms 50ms

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Real World left +=10 left +=10 left +=10 left +=10 left +=10 10ms 25ms 41ms 53ms 68ms

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Smooth Animation • Get time period on every call

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Smooth~ left +=10 left +=15 left +=16 left +=12 left +=15 10ms 25ms 41ms 53ms 68ms

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Libraries • Library can make smooth animation

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Race Condition • We want to fade something out then fade it in

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var info = document.getElementById('info');! ! fadeOut(info);! fadeIn(info);

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... • Not fade in • Inﬁnity loop • If we use time period on each call • Not inﬁnity loop • Animation is ugly

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Solution • Callback function

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Callback $('#info').fadeOut(function () {! $(this).fadeIn();! });

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jQuery fade $('#info').fadeOut();! $('#info').fadeIn();

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The Queue • Traditional queue • Solves race condition

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.queue() $('#info').queue('qName', function () {! //things to do next! ! $(this).dequeue();! });

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Animate and Queue • .animate always use ‘fx’ as its queue name • .queue has default queue name: ‘fx’

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If Boss Want • Fade Out • Change content • Fade In • Move right 500 pixel • Add class ‘active’ • Move left 500 pixel • Change content again

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Callbacks $('#id').fadeOut(function () {! $(this).html('new content');! $(this).fadeIn(function () {! $(this).animate({left: '+=500'}, function () {! $(this).addClass('active');! $(this).animate({left: '-=500'}, function () {! $(this).html('even new content');! });! });! });! });

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Queue $('#id')! .fadeOut()! .queue(function () {! $(this).html('new content');! $(this).dequeue();! })! .fadeIn()! .animate({left: '+=500'})! .queue(function () {! $(this).addClass('active');! $(this).dequeue();! })! .animate({left: '-=500'})! .queue(function () {! $(this).html('even new content');! $(this).dequeue();! });

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Advantages • Less indent • Delay or clear queue is much easier • Better for maintain • What happens if boss want to change spec

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If I Want To • Fade out A, B, C by order

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$('#A').fadeOut();! $('#B').fadeOut();! $('#C').fadeOut(); W rong

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$('#A').fadeOut(function () {! $('#B').fadeOut(function () {! $('#C').fadeOut();! });! });

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$('#A')! .fadeOut()! .queue(function () {! var $that = $(this);! $('#B').fadeOut(function () {! $that.dequeue();! });! })! .queue(function () {! var $that = $(this);! $('#C').fadeOut(function () {! $that.dequeue();! });! });

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$({}).queue(function () {! var $that = $(this);! $('#A').fadeOut(function () {! $that.dequeue();! });! }).queue(function () {! var $that = $(this);! $('#B').fadeOut(function () {! $that.dequeue();! });! }).queue(function () {! var $that = $(this);! $('#C').fadeOut(function () {! $that.dequeue();! });! });

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$({}).queue(function (next) {! $('#A').fadeOut(next);! }).queue(function (next) {! $('#B').fadeOut(next);! }).queue(function (next) {! $('#C').fadeOut(next);! });

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$('#A').fadeOut().queue(function (next) {! $('#B').fadeOut(next);! }).queue(function (next) {! $('#C').fadeOut(next);! });

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Deferred http://www.ﬂickr.com/photos/gozalewis/3256814461/

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History • a.k.a Promise • Idea since 1976 (Call by future) • Dojo 0.9 (2007), 1.5 (2010) • jQuery 1.5 (2011) • CommonJS Promises/A

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What is Deferred • In computer science, future, promise, and delay refer to constructs used for synchronization in some concurrent programming languages. http://en.wikipedia.org/wiki/Futures_and_promises

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get account render page redirect login status wait result wait result wait result

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jQuery Deferred • Multiple handler functions • Register handlers at any time • jQuery.when http://api.jquery.com/category/deferred-object/

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Example: Image Loader function imgLoader(src) {! var _img = new Image(),! _dfd = $.Deferred();! ! _img.onload = _dfd.resolve; //success! _img.onerror = _dfd.reject; //fail! ! _img.src = src! ! return _dfd.promise();! }

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Image Loader image fade out image render page Deferred

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render page image Deferred .promise() resolve reject fade out image fail done Image Loader

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Use Image Loader imgLoader('/images/logo.png').done(function () {! ! $('#logo').fadeIn();! ! }).fail(function () {! ! document.location = '/404.html';! ! });

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Use Image Loader var logo_dfd = imgLoader('/images/logo.png');! ! logo_dfd.done(function () {! $('#logo').fadeIn();! }).fail(function () {! document.location = '/404.html';! });! ! //Some place else! logo_dfd.done(function () {! App.init();! });! ! //Another place ! logo_dfd.fail(function () {! App.destroy();! });

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jQuery.when $.when(! ! $.getJSON('/api/jedis'),! $.getJSON('/api/siths'),! $.getJSON('/api/terminators')! ! ).done(function (jedis, siths, terminators) {! ! // do something....! ! });

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Complex Dependency data device async async render account async

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var account = $.getJSON('/api/account');! var device = account.pipe(function () {! $.getJSON('/api/device');! });! ! var data = $.when(account, device).pipe(function () {! $.getJSON('/api/data');! });! ! $.when(account, device, data).done(render);

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Advantages • Manage handlers • Cache results • $.when solves complex async dependency

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Advance Feature • pipe

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Not to Talk Today

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Callbacks http://www.ﬂickr.com/photos/inkytwist/3708782412/

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Callbacks • A multi-purpose callbacks list object that provides a powerful way to manage callback lists

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How to Use function fn( value ){! console.log( value );! }! ! var callbacks = $.Callbacks();! callbacks.add( fn );! callbacks.fire( "foo!" );

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Methods • add • remove • has • fire • fireWith • fired • lock • locked • disable • disabled • empty

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Flags • once • memory • unique • stopOnFalse

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once • Can only be ﬁred once

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once function fn1( value ) {! console.log( value );! }! ! var callbacks = $.Callbacks('once');! callbacks.add( fn1 );! callbacks.fire( "foo!" ); // foo!! callbacks.fire( "foo!" ); //

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memory • Remember the arguments you give

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memory function fn1( value ) {! console.log( value );! }! function fn2() {! console.log( '2' );! }! ! var callbacks = $.Callbacks('memory');! callbacks.add( fn1 );! callbacks.fire( "foo!" ); // foo!! callbacks.add( fn1 ); // foo!! callbacks.add( fn2 ); // 2! callbacks.fire( "bar!" ); // bar!, bar!, 2

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once memory function fn1( value ) {! console.log( value );! }! function fn2() {! console.log( '2' );! }! ! var callbacks = $.Callbacks('once memory');! callbacks.add( fn1 );! callbacks.fire( "foo!" ); // foo!! callbacks.add( fn1 ); // foo!! callbacks.add( fn2 ); // 2! callbacks.fire( "bar!" ); //

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unique • Ensure all callback function are unique

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unique function fn1( value ) {! console.log( value );! }! function fn2() {! console.log( '2' );! }! ! var callbacks = $.Callbacks('unique');! callbacks.add( fn1 );! callbacks.add( fn1 ); ! callbacks.add( fn2 );! callbacks.fire( "foo!" ); // foo!, 2

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stopOnFalse • Stop if a function returns false

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Deferred • Use ‘once memory’

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When to Use • If you have to manage callback functions • If you need any feature of the ﬂags • If you want to break down your codes

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Use Case • jQuery Deferred Object • PubSub by Addy Osmani

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Questions?

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PubSub var topics = {};! ! jQuery.Topic = function( id ) {! var callbacks,! topic = id && topics[ id ];! if ( !topic ) {! callbacks = jQuery.Callbacks();! topic = {! publish: callbacks.fire,! subscribe: callbacks.add,! unsubscribe: callbacks.remove! };! if ( id ) {! topics[ id ] = topic;! }! }! return topic;! }; http://addyosmani.com/blog/jquery-1-7s-callbacks-feature-demystiﬁed/

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References • http://api.jquery.com/queue/ • http://api.jquery.com/category/deferred-object/ • http://api.jquery.com/jQuery.Callbacks/ • http://addyosmani.com/blog/jquery-1-7s-callbacks- feature-demystiﬁed/

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Thank You