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  <div id="sidebar" class="interface">

    <a class="toc_title" href="#">
      Backbone.js <span class="version">(0.9.2)</span>
    </a>
    <ul class="toc_section">
      <li>&raquo; <a href="http://github.com/documentcloud/backbone">GitHub Repository</a></li>
      <li>&raquo; <a href="docs/backbone.html">Annotated Source</a></li>
    </ul>

    <a class="toc_title" href="#introduction">
      Introduction
    </a>

    <a class="toc_title" href="#upgrading">
      Upgrading
    </a>

    <a class="toc_title" href="#Events">
      Events
    </a>
    <ul class="toc_section">
      <li>– <a href="#Events-on">on</a></li>
      <li>– <a href="#Events-off">off</a></li>
      <li>– <a href="#Events-trigger">trigger</a></li>
    </ul>

    <a class="toc_title" href="#Model">
      Model
    </a>
    <ul class="toc_section">
      <li>– <a href="#Model-extend">extend</a></li>
      <li>– <a href="#Model-constructor">constructor / initialize</a></li>
      <li>– <a href="#Model-get">get</a></li>
      <li>– <a href="#Model-set">set</a></li>
      <li>– <a href="#Model-escape">escape</a></li>
      <li>– <a href="#Model-has">has</a></li>
      <li>– <a href="#Model-unset">unset</a></li>
      <li>– <a href="#Model-clear">clear</a></li>
      <li>– <a href="#Model-id">id</a></li>
      <li>– <a href="#Model-idAttribute">idAttribute</a></li>
      <li>– <a href="#Model-cid">cid</a></li>
      <li>– <a href="#Model-attributes">attributes</a></li>
      <li>– <a href="#Model-changed">changed</a></li>
      <li>– <a href="#Model-defaults">defaults</a></li>
      <li>– <a href="#Model-toJSON">toJSON</a></li>
      <li>– <a href="#Model-sync">sync</a></li>
      <li>– <a href="#Model-fetch">fetch</a></li>
      <li>– <a href="#Model-save">save</a></li>
      <li>– <a href="#Model-destroy">destroy</a></li>
      <li>– <a href="#Model-validate">validate</a></li>
      <li>– <a href="#Model-isValid">isValid</a></li>
      <li>– <a href="#Model-url">url</a></li>
      <li>– <a href="#Model-urlRoot">urlRoot</a></li>
      <li>– <a href="#Model-parse">parse</a></li>
      <li>– <a href="#Model-clone">clone</a></li>
      <li>– <a href="#Model-isNew">isNew</a></li>
      <li>– <a href="#Model-change">change</a></li>
      <li>– <a href="#Model-hasChanged">hasChanged</a></li>
      <li>– <a href="#Model-changedAttributes">changedAttributes</a></li>
      <li>– <a href="#Model-previous">previous</a></li>
      <li>– <a href="#Model-previousAttributes">previousAttributes</a></li>
    </ul>

    <a class="toc_title" href="#Collection">
      Collection
    </a>
    <ul class="toc_section">
      <li>– <a href="#Collection-extend">extend</a></li>
      <li>– <a href="#Collection-model">model</a></li>
      <li>– <a href="#Collection-constructor">constructor / initialize</a></li>
      <li>– <a href="#Collection-models">models</a></li>
      <li>– <a href="#Collection-toJSON">toJSON</a></li>
      <li>– <a href="#Collection-sync">sync</a></li>
      <li>– <a href="#Collection-Underscore-Methods"><b>Underscore Methods (28)</b></a></li>
      <li>– <a href="#Collection-add">add</a></li>
      <li>– <a href="#Collection-remove">remove</a></li>
      <li>– <a href="#Collection-get">get</a></li>
      <li>– <a href="#Collection-getByCid">getByCid</a></li>
      <li>– <a href="#Collection-at">at</a></li>
      <li>– <a href="#Collection-push">push</a></li>
      <li>– <a href="#Collection-pop">pop</a></li>
      <li>– <a href="#Collection-unshift">unshift</a></li>
      <li>– <a href="#Collection-shift">shift</a></li>
      <li>– <a href="#Collection-length">length</a></li>
      <li>– <a href="#Collection-comparator">comparator</a></li>
      <li>– <a href="#Collection-sort">sort</a></li>
      <li>– <a href="#Collection-pluck">pluck</a></li>
      <li>– <a href="#Collection-where">where</a></li>
      <li>– <a href="#Collection-url">url</a></li>
      <li>– <a href="#Collection-parse">parse</a></li>
      <li>– <a href="#Collection-clone">clone</a></li>
      <li>– <a href="#Collection-fetch">fetch</a></li>
      <li>– <a href="#Collection-reset">reset</a></li>
      <li>– <a href="#Collection-create">create</a></li>
    </ul>

    <a class="toc_title" href="#Router">
      Router
    </a>
    <ul class="toc_section">
      <li>– <a href="#Router-extend">extend</a></li>
      <li>– <a href="#Router-routes">routes</a></li>
      <li>– <a href="#Router-constructor">constructor / initialize</a></li>
      <li>– <a href="#Router-route">route</a></li>
      <li>– <a href="#Router-navigate">navigate</a></li>
    </ul>

    <a class="toc_title" href="#History">
      History
    </a>
    <ul class="toc_section">
      <li>– <a href="#History-start">start</a></li>
    </ul>

    <a class="toc_title" href="#Sync">
      Sync
    </a>
    <ul class="toc_section">
      <li>– <a href="#Sync">Backbone.sync</a></li>
      <li>– <a href="#Sync-ajax">Backbone.ajax</a></li>
      <li>– <a href="#Sync-emulateHTTP">Backbone.emulateHTTP</a></li>
      <li>– <a href="#Sync-emulateJSON">Backbone.emulateJSON</a></li>
    </ul>

    <a class="toc_title" href="#View">
      View
    </a>
    <ul class="toc_section">
      <li>– <a href="#View-extend">extend</a></li>
      <li>– <a href="#View-constructor">constructor / initialize</a></li>
      <li>– <a href="#View-el">el</a></li>
      <li>– <a href="#View-$el">$el</a></li>
      <li>– <a href="#View-setElement">setElement</a></li>
      <li>– <a href="#View-attributes">attributes</a></li>
      <li>– <a href="#View-dollar">$ (jQuery or Zepto)</a></li>
      <li>– <a href="#View-render">render</a></li>
      <li>– <a href="#View-remove">remove</a></li>
      <li>– <a href="#View-dispose">dispose</a></li>
      <li>– <a href="#View-make">make</a></li>
      <li>– <a href="#View-delegateEvents">delegateEvents</a></li>
      <li>– <a href="#View-undelegateEvents">undelegateEvents</a></li>
    </ul>

    <a class="toc_title" href="#Utility">
      Utility
    </a>
    <ul class="toc_section">
      <li>– <a href="#Utility-Backbone-noConflict">Backbone.noConflict</a></li>
      <li>– <a href="#Utility-Backbone-$">Backbone.$</a></li>
    </ul>

    <a class="toc_title" href="#examples">
      Examples
    </a>
    <ul class="toc_section">
      <li>– <a href="#examples-todos">Todos</a></li>
      <li>– <a href="#examples-documentcloud">DocumentCloud</a></li>
      <li>– <a href="#examples-rdio">Rdio</a></li>
      <li>– <a href="#examples-linkedin">LinkedIn Mobile</a></li>
      <li>– <a href="#examples-flow">Flow</a></li>
      <li>– <a href="#examples-wordpress">WordPress.com</a></li>
      <li>– <a href="#examples-foursquare">Foursquare</a></li>
      <li>– <a href="#examples-wunderkit">Wunderkit</a></li>
      <li>– <a href="#examples-disqus">Disqus</a></li>
      <li>– <a href="#examples-khan-academy">Khan Academy</a></li>
      <li>– <a href="#examples-do">Do</a></li>
      <li>– <a href="#examples-pitchfork">Pitchfork</a></li>
      <li>– <a href="#examples-spin">Spin</a></li>
      <li>– <a href="#examples-walmart">Walmart Mobile</a></li>
      <li>– <a href="#examples-groupon">Groupon Now!</a></li>
      <li>– <a href="#examples-basecamp">Basecamp Mobile</a></li>
      <li>– <a href="#examples-slavery-footprint">Slavery Footprint</a></li>
      <li>– <a href="#examples-stripe">Stripe</a></li>
      <li>– <a href="#examples-airbnb">Airbnb</a></li>
      <li>– <a href="#examples-diaspora">Diaspora</a></li>
      <li>– <a href="#examples-soundcloud">SoundCloud Mobile</a></li>
      <li>- <a href="#examples-artsy">Art.sy</a></li>
      <li>– <a href="#examples-pandora">Pandora</a></li>
      <li>– <a href="#examples-inkling">Inkling</a></li>
      <li>– <a href="#examples-code-school">Code School</a></li>
      <li>– <a href="#examples-cloudapp">CloudApp</a></li>
      <li>– <a href="#examples-seatgeek">SeatGeek</a></li>
      <li>– <a href="#examples-easel">Easel</a></li>
      <li>– <a href="#examples-prose">Prose</a></li>
      <li>– <a href="#examples-grove">Grove.io</a></li>
      <li>– <a href="#examples-kanogames">KANO/GAMES</a></li>
      <li>– <a href="#examples-shortmail">Shortmail</a></li>
      <li>– <a href="#examples-scrollkit">scroll kit</a></li>
      <li>– <a href="#examples-battlefield">Battlefield Play4Free</a></li>
      <li>– <a href="#examples-salon">Salon.io</a></li>
      <li>– <a href="#examples-tilemill">TileMill</a></li>
      <li>– <a href="#examples-blossom">Blossom</a></li>
      <li>– <a href="#examples-decide">Decide</a></li>
      <li>– <a href="#examples-trello">Trello</a></li>
      <li>– <a href="#examples-ducksboard">Ducksboard</a></li>
      <li>– <a href="#examples-quietwrite">QuietWrite</a></li>
      <li>– <a href="#examples-tzigla">Tzigla</a></li>
    </ul>

    <a class="toc_title" href="#faq">
      F.A.Q.
    </a>
    <ul class="toc_section">
      <li>– <a href="#FAQ-events">Catalog of Events</a></li>
      <li>– <a href="#FAQ-tim-toady">More Than One Way To Do It</a></li>
      <li>– <a href="#FAQ-nested">Nested Models &amp; Collections</a></li>
      <li>– <a href="#FAQ-bootstrap">Loading Bootstrapped Models</a></li>
      <li>– <a href="#FAQ-extending">Extending Backbone</a></li>
      <li>– <a href="#FAQ-mvc">Traditional MVC</a></li>
      <li>– <a href="#FAQ-this">Binding "this"</a></li>
      <li>– <a href="#FAQ-rails">Working with Rails</a></li>
    </ul>

    <a class="toc_title" href="#changelog">
      Change Log
    </a>

  </div>

  <div class="container">

    <p>
      <img id="logo" src="docs/images/backbone.png" alt="Backbone.js" />
    </p>

    <p>
      Backbone.js gives structure to web applications
      by providing <b>models</b> with key-value binding and custom events,
      <b>collections</b> with a rich API of enumerable functions,
      <b>views</b> with declarative event handling, and connects it all to your
      existing API over a RESTful JSON interface.
    </p>

    <p>
      The project is <a href="http://github.com/documentcloud/backbone/">hosted on GitHub</a>,
      and the <a href="docs/backbone.html">annotated source code</a> is available,
      as well as an online <a href="test/">test suite</a>,
      an <a href="examples/todos/index.html">example application</a>,
      a <a href="https://github.com/documentcloud/backbone/wiki/Tutorials%2C-blog-posts-and-example-sites">list of tutorials</a>
      and a <a href="#examples">long list of real-world projects</a> that use Backbone.
      Backbone is available for use under the <a href="http://github.com/documentcloud/backbone/blob/master/LICENSE">MIT software license</a>.
    </p>

    <p>
      You can report bugs and discuss features on the
      <a href="http://github.com/documentcloud/backbone/issues">GitHub issues page</a>,
      on Freenode IRC in the <tt>#documentcloud</tt> channel, post questions to the
      <a href="https://groups.google.com/forum/#!forum/backbonejs">Google Group</a>,
      add pages to the <a href="https://github.com/documentcloud/backbone/wiki">wiki</a>
      or send tweets to <a href="http://twitter.com/documentcloud">@documentcloud</a>.
    </p>

    <p>
      <i>
        Backbone is an open-source component of
        <a href="http://documentcloud.org/">DocumentCloud</a>.
      </i>
    </p>

    <h2 id="downloads">
      Downloads &amp; Dependencies
      <span style="padding-left: 7px; font-size:11px; font-weight: normal;" class="interface">(Right-click, and use "Save As")</span>
    </h2>

    <table>
      <tr>
        <td><a class="punch" href="backbone.js">Development Version (0.9.2)</a></td>
        <td class="text"><i>52kb, Full source, lots of comments</i></td>
      </tr>
      <tr>
        <td><a class="punch" href="backbone-min.js">Production Version (0.9.2)</a></td>
        <td class="text"><i>5.6kb, Packed and gzipped</i></td>
      </tr>
      <tr>
        <td><a class="punch" href="https://raw.github.com/documentcloud/backbone/master/backbone.js">Edge Version (master)</a></td>
        <td><i>Unreleased, use at your own risk</i></td>
      </tr>
    </table>

    <p>
      Backbone's only hard dependency is
      <a href="http://underscorejs.org/">Underscore.js</a> <small>( > 1.3.1)</small>.
      For RESTful persistence, history support via <a href="#Router">Backbone.Router</a>
      and DOM manipulation with <a href="#View">Backbone.View</a>, include
      <a href="https://github.com/douglascrockford/JSON-js">json2.js</a>, and either
      <a href="http://jquery.com">jQuery</a> <small>( > 1.4.2)</small> or
      <a href="http://zeptojs.com/">Zepto</a>.
    </p>

    <h2 id="introduction">Introduction</h2>

    <p>
      When working on a web application that involves a lot of JavaScript, one
      of the first things you learn is to stop tying your data to the DOM. It's all
      too easy to create JavaScript applications that end up as tangled piles of
      jQuery selectors and callbacks, all trying frantically to keep data in
      sync between the HTML UI, your JavaScript logic, and the database on your
      server. For rich client-side applications, a more structured approach
      is often helpful.
    </p>

    <p>
      With Backbone, you represent your data as
      <a href="#Model">Models</a>, which can be created, validated, destroyed,
      and saved to the server. Whenever a UI action causes an attribute of
      a model to change, the model triggers a <i>"change"</i> event; all
      the <a href="#View">Views</a> that display the model's state can be notified of the
      change, so that they are able to respond accordingly, re-rendering themselves with
      the new information. In a finished Backbone app, you don't have to write the glue
      code that looks into the DOM to find an element with a specific <i>id</i>,
      and update the HTML manually
      &mdash; when the model changes, the views simply update themselves.
    </p>

    <p>
      If you're new here, and aren't yet quite sure what Backbone is for, start by
      browsing the <a href="#examples">list of Backbone-based projects</a>.
    </p>

    <p>
      Many of the examples that follow are runnable. Click the <i>play</i> button
      to execute them.
    </p>

    <h2 id="upgrading">Upgrading to 0.9</h2>

    <p>
      Backbone's <b>0.9</b> series should be considered as a release candidate
      for an upcoming <b>1.0</b>. Some APIs have changed, and while there is a
      <a href="#changelog">change log</a> available, and many new features to
      take advantage of, there are a few specific changes where you'll need
      to take care:
    </p>

    <ul>
      <li>
        If you've ever manually set <tt>this.el</tt> in a Backbone View to be a
        particular DOM element, you'll want to use
        <a href="#View-setElement">setElement</a> instead.
      </li>
      <li>
        Creating and destroying models is now optimistic. Pass <tt>{wait: true}</tt>
        if you need the previous behavior of waiting for the server to acknowledge
        success. You can now also pass <tt>{wait: true}</tt> to <a href="#Model-save">save</a> calls.
      </li>
      <li>
        If you have been writing a fair amount of <tt>$(view.el)</tt>, there's now
        a cached reference for that jQuery object: <a href="#View-$el">$el</a>.
      </li>
      <li>
        If you're upgrading, make sure you also upgrade your version of Underscore.js
        to the latest &mdash; 1.3.1 or greater.
      </li>
      <li>
        <tt>model.set</tt> will no longer trigger change events when setting a value
        with <tt>{silent: true}</tt> then setting it back to its original value.
        Similarly, after changing an attribute silently, that <tt>change:attribute</tt>
        event <i>will</i> fire during the next change.
      </li>
      <li>
        Since <tt>view.$(selector)</tt> is now equivalent to <tt>view.$el.find(selector)</tt>
        rather than <tt>$(selector, view.el)</tt> it can no longer be used when
        <tt>selector</tt> is an HTML string or DOM element.
      </li>
    </ul>

    <h2 id="Events">Backbone.Events</h2>

    <p>
      <b>Events</b> is a module that can be mixed in to any object, giving the
      object the ability to bind and trigger custom named events. Events do not
      have to be declared before they are bound, and may take passed arguments.
      For example:
    </p>

<pre class="runnable">
var object = {};

_.extend(object, Backbone.Events);

object.on("alert", function(msg) {
  alert("Triggered " + msg);
});

object.trigger("alert", "an event");
</pre>

    <p>
      For example, to make a handy event dispatcher that can coordinate events
      among different areas of your application: <tt>var dispatcher = _.clone(Backbone.Events)</tt>
    </p>

    <p id="Events-on">
      <b class="header">on</b><code>object.on(event, callback, [context])</code><span class="alias">Alias: bind</span>
      <br />
      Bind a <b>callback</b> function to an object. The callback will be invoked
      whenever the <b>event</b> is fired.
      If you have a large number of different events on a page, the convention is to use colons to
      namespace them: <tt>"poll:start"</tt>, or <tt>"change:selection"</tt>.
      The event string may also be a space-delimited list of several events...
    </p>

<pre>
book.on("change:title change:author", ...);
</pre>

    <p>
      To supply a <b>context</b> value for <tt>this</tt> when the callback is invoked,
      pass the optional third argument: <tt>model.on('change', this.render, this)</tt>
    </p>

    <p>
      Callbacks bound to the special
      <tt>"all"</tt> event will be triggered when any event occurs, and are passed
      the name of the event as the first argument. For example, to proxy all events
      from one object to another:
    </p>

<pre>
proxy.on("all", function(eventName) {
  object.trigger(eventName);
});
</pre>

    <p id="Events-off">
      <b class="header">off</b><code>object.off([event], [callback], [context])</code><span class="alias">Alias: unbind</span>
      <br />
      Remove a previously-bound <b>callback</b> function from an object. If no
      <b>context</b> is specified, all of the versions of the callback with
      different contexts will be removed. If no
      callback is specified, all callbacks for the <b>event</b> will be
      removed. If no event is specified, callbacks for <i>all</i> events
      will be removed.
    </p>

<pre>
// Removes just the `onChange` callback.
object.off("change", onChange);

// Removes all "change" callbacks.
object.off("change");

// Removes the `onChange` callback for all events.
object.off(null, onChange);

// Removes all callbacks for `context` for all events.
object.off(null, null, context);

// Removes all callbacks on `object`.
object.off();
</pre>

    <p id="Events-trigger">
      <b class="header">trigger</b><code>object.trigger(event, [*args])</code>
      <br />
      Trigger callbacks for the given <b>event</b>, or space-delimited list of events.
      Subsequent arguments to <b>trigger</b> will be passed along to the
      event callbacks.
    </p>

    <h2 id="Model">Backbone.Model</h2>

    <p>
      <b>Models</b> are the heart of any JavaScript application, containing
      the interactive data as well as a large part of the logic surrounding it:
      conversions, validations, computed properties, and access control. You
      extend <b>Backbone.Model</b> with your domain-specific methods, and
      <b>Model</b> provides a basic set of functionality for managing changes.
    </p>

    <p>
      The following is a contrived example, but it demonstrates defining a model
      with a custom method, setting an attribute, and firing an event keyed
      to changes in that specific attribute.
      After running this code once, <tt>sidebar</tt> will be
      available in your browser's console, so you can play around with it.
    </p>

<pre class="runnable">
var Sidebar = Backbone.Model.extend({
  promptColor: function() {
    var cssColor = prompt("Please enter a CSS color:");
    this.set({color: cssColor});
  }
});

window.sidebar = new Sidebar;

sidebar.on('change:color', function(model, color) {
  $('#sidebar').css({background: color});
});

sidebar.set({color: 'white'});

sidebar.promptColor();
</pre>

    <p id="Model-extend">
      <b class="header">extend</b><code>Backbone.Model.extend(properties, [classProperties])</code>
      <br />
      To create a <b>Model</b> class of your own, you extend <b>Backbone.Model</b>
      and provide instance <b>properties</b>, as well as optional
      <b>classProperties</b> to be attached directly to the constructor function.
    </p>

    <p>
      <b>extend</b> correctly sets up the prototype chain, so subclasses created
      with <b>extend</b> can be further extended and subclassed as far as you like.
    </p>

<pre>
var Note = Backbone.Model.extend({

  initialize: function() { ... },

  author: function() { ... },

  coordinates: function() { ... },

  allowedToEdit: function(account) {
    return true;
  }

});

var PrivateNote = Note.extend({

  allowedToEdit: function(account) {
    return account.owns(this);
  }

});
</pre>

    <p class="warning">
        Brief aside on <tt>super</tt>: JavaScript does not provide
        a simple way to call super &mdash; the function of the same name defined
        higher on the prototype chain. If you override a core function like
        <tt>set</tt>, or <tt>save</tt>, and you want to invoke the
        parent object's implementation, you'll have to explicitly call it, along these lines:
    </p>

<pre>
var Note = Backbone.Model.extend({
  set: function(attributes, options) {
    Backbone.Model.prototype.set.apply(this, arguments);
    ...
  }
});
</pre>

    <p id="Model-constructor">
      <b class="header">constructor / initialize</b><code>new Model([attributes], [options])</code>
      <br />
      When creating an instance of a model, you can pass in the initial values
      of the <b>attributes</b>, which will be <a href="#Model-set">set</a> on the
      model. If you define an <b>initialize</b> function, it will be invoked when
      the model is created.
    </p>

<pre>
new Book({
  title: "One Thousand and One Nights",
  author: "Scheherazade"
});
</pre>

    <p>
      In rare cases, if you're looking to get fancy,
      you may want to override <b>constructor</b>, which allows
      you to replace the actual constructor function for your model.
    </p>

    <p>
      If you pass a <tt>{collection: ...}</tt> as the <b>options</b>, the model
      gains a <tt>collection</tt> property that will be used to indicate which
      collection the model belongs to, and is used to help compute the model's
      <a href="#Model-url">url</a>. The <tt>model.collection</tt> property is
      otherwise added automatically when you first add a model to a collection.
    </p>

    <p id="Model-get">
      <b class="header">get</b><code>model.get(attribute)</code>
      <br />
      Get the current value of an attribute from the model. For example:
      <tt>note.get("title")</tt>
    </p>

    <p id="Model-set">
      <b class="header">set</b><code>model.set(attributes, [options])</code>
      <br />
      Set a hash of attributes (one or many) on the model. If any of the attributes
      change the model's state, a <tt>"change"</tt> event will be triggered, unless
      <tt>{silent: true}</tt> is passed as an option. Change events for specific
      attributes are also triggered, and you can bind to those as well, for example:
      <tt>change:title</tt>, and <tt>change:content</tt>. You may also pass
      individual keys and values.
    </p>

<pre>
note.set({title: "March 20", content: "In his eyes she eclipses..."});

book.set("title", "A Scandal in Bohemia");
</pre>

    <p>
      If the model has a <a href="#Model-validate">validate</a> method,
      it will be validated before the attributes are set, no changes will
      occur if the validation fails, and <b>set</b> will return <tt>false</tt>.
      Otherwise, <b>set</b> returns a reference to the model.
      You may also pass an <tt>error</tt>
      callback in the options, which will be invoked instead of triggering an
      <tt>"error"</tt> event, should validation fail.
      If <tt>{silent: true}</tt> is passed as an option, the validation is deferred
      until the next change.
    </p>

    <p id="Model-escape">
      <b class="header">escape</b><code>model.escape(attribute)</code>
      <br />
      Similar to <a href="#Model-get">get</a>, but returns the HTML-escaped version
      of a model's attribute. If you're interpolating data from the model into
      HTML, using <b>escape</b> to retrieve attributes will prevent
      <a href="http://en.wikipedia.org/wiki/Cross-site_scripting">XSS</a> attacks.
    </p>

<pre class="runnable">
var hacker = new Backbone.Model({
  name: "&lt;script&gt;alert('xss')&lt;/script&gt;"
});

alert(hacker.escape('name'));
</pre>

    <p id="Model-has">
      <b class="header">has</b><code>model.has(attribute)</code>
      <br />
      Returns <tt>true</tt> if the attribute is set to a non-null or non-undefined
      value.
    </p>

<pre>
if (note.has("title")) {
  ...
}
</pre>

    <p id="Model-unset">
      <b class="header">unset</b><code>model.unset(attribute, [options])</code>
      <br />
      Remove an attribute by deleting it from the internal attributes hash.
      Fires a <tt>"change"</tt> event unless <tt>silent</tt> is passed as an option.
    </p>

    <p id="Model-clear">
      <b class="header">clear</b><code>model.clear([options])</code>
      <br />
      Removes all attributes from the model, including the <tt>id</tt> attribute. Fires a <tt>"change"</tt> event unless
      <tt>silent</tt> is passed as an option.
    </p>

    <p id="Model-id">
      <b class="header">id</b><code>model.id</code>
      <br />
      A special property of models, the <b>id</b> is an arbitrary string
      (integer id or UUID). If you set the <b>id</b> in the
      attributes hash, it will be copied onto the model as a direct property.
      Models can be retrieved by id from collections, and the id is used to generate
      model URLs by default.
    </p>

    <p id="Model-idAttribute">
      <b class="header">idAttribute</b><code>model.idAttribute</code>
      <br />
      A model's unique identifier is stored under the <tt>id</tt> attribute.
      If you're directly communicating with a backend (CouchDB, MongoDB) that uses
      a different unique key, you may set a Model's <tt>idAttribute</tt> to
      transparently map from that key to <tt>id</tt>.

<pre class="runnable">
var Meal = Backbone.Model.extend({
  idAttribute: "_id"
});

var cake = new Meal({ _id: 1, name: "Cake" });
alert("Cake id: " + cake.id);
</pre>
    </p>

    <p id="Model-cid">
      <b class="header">cid</b><code>model.cid</code>
      <br />
      A special property of models, the <b>cid</b> or client id is a unique identifier
      automatically assigned to all models when they're first created. Client ids
      are handy when the model has not yet been saved to the server, and does not
      yet have its eventual true <b>id</b>, but already needs to be visible in the UI.
      Client ids take the form: <tt>c1, c2, c3 ...</tt>
    </p>

    <p id="Model-attributes">
      <b class="header">attributes</b><code>model.attributes</code>
      <br />
      The <b>attributes</b> property is the internal hash containing the model's
      state &mdash; usually (but not necessarily) a form of the JSON object
      representing the model data on the server. It's often a straightforward
      serialization of a row from the database, but it could also be client-side
      computed state.
    </p>

    <p>
      Please use <a href="#Model-set">set</a> to update the <b>attributes</b>
      instead of modifying them directly. If you'd like to retrieve and munge a
      copy of the model's attributes, use <a href="#Model-toJSON">toJSON</a>
      instead.
    </p>

    <p class="warning">
      Due to the fact that <a href="#Events">Events</a> accepts space separated
      lists of events, attribute names should not include spaces.
    </p>

    <p id="Model-changed">
      <b class="header">changed</b><code>model.changed</code>
      <br />
      The <b>changed</b> property is the internal hash containing all the attributes
      that have changed since the last <tt>"change"</tt> event was triggered.
      Please do not update <b>changed</b> directly.  Its state is maintained internally
      by <a href="#Model-set">set</a> and <a href="#Model-change">change</a>.
      A copy of <b>changed</b> can be acquired from
      <a href="#Model-changedAttributes">changedAttributes</a>.
    </p>

    <p id="Model-defaults">
      <b class="header">defaults</b><code>model.defaults or model.defaults()</code>
      <br />
      The <b>defaults</b> hash (or function) can be used to specify the default
      attributes for your model. When creating an instance of the model,
      any unspecified attributes will be set to their default value.
    </p>

<pre class="runnable">
var Meal = Backbone.Model.extend({
  defaults: {
    "appetizer":  "caesar salad",
    "entree":     "ravioli",
    "dessert":    "cheesecake"
  }
});

alert("Dessert will be " + (new Meal).get('dessert'));
</pre>

    <p class="warning">
      Remember that in JavaScript, objects are passed by reference, so if you
      include an object as a default value, it will be shared among all instances.
      Instead, define <b>defaults</b> as a function.
    </p>

    <p id="Model-toJSON">
      <b class="header">toJSON</b><code>model.toJSON()</code>
      <br />
      Return a copy of the model's <a href="#Model-attributes">attributes</a> for JSON stringification.
      This can be used for persistence, serialization, or for augmentation before
      being handed off to a view. The name of this method is a bit confusing, as
      it doesn't actually return a JSON string &mdash; but I'm afraid that it's
      the way that the <a href="https://developer.mozilla.org/en/JSON#toJSON()_method">JavaScript API for <b>JSON.stringify</b> works</a>.
    </p>

<pre class="runnable">
var artist = new Backbone.Model({
  firstName: "Wassily",
  lastName: "Kandinsky"
});

artist.set({birthday: "December 16, 1866"});

alert(JSON.stringify(artist));
</pre>

    <p id="Model-sync">
      <b class="header">sync</b><code>model.sync(method, model, [options])</code>
      <br />
      Uses <a href="#Sync">Backbone.sync</a> to persist the state of a model to
      the server.  Can be overridden for custom behavior.
    </p>

    <p id="Model-fetch">
      <b class="header">fetch</b><code>model.fetch([options])</code>
      <br />
      Resets the model's state from the server by delegating to
      <a href="#Sync">Backbone.sync</a>. Returns a
      <a href="http://api.jquery.com/jQuery.ajax/#jqXHR">jqXHR</a>.
      Useful if the model has never
      been populated with data, or if you'd like to ensure that you have the
      latest server state. A <tt>"change"</tt> event will be triggered if the
      server's state differs from the current attributes. Accepts
      <tt>success</tt> and <tt>error</tt> callbacks in the options hash, which
      are passed <tt>(model, response)</tt> as arguments.
    </p>

<pre>
// Poll every 10 seconds to keep the channel model up-to-date.
setInterval(function() {
  channel.fetch();
}, 10000);
</pre>

    <p id="Model-save">
      <b class="header">save</b><code>model.save([attributes], [options])</code>
      <br />
      Save a model to your database (or alternative persistence layer),
      by delegating to <a href="#Sync">Backbone.sync</a>.  Returns a
      <a href="http://api.jquery.com/jQuery.ajax/#jqXHR">jqXHR</a> if
      validation is successful and <tt>false</tt> otherwise. The <b>attributes</b>
      hash (as in <a href="#Model-set">set</a>) should contain the attributes
      you'd like to change &mdash; keys that aren't mentioned won't be altered &mdash; but,
      a <i>complete representation</i> of the resource will be sent to the server.
      As with <tt>set</tt>, you may pass individual keys and values instead of a hash.
      If the model has a <a href="#Model-validate">validate</a>
      method, and validation fails, the model will not be saved. If the model
      <a href="#Model-isNew">isNew</a>, the save will be a <tt>"create"</tt>
      (HTTP <tt>POST</tt>), if the model already
      exists on the server, the save will be an <tt>"update"</tt> (HTTP <tt>PUT</tt>).
    </p>

    <p>
      Calling <tt>save</tt> with new attributes will cause a <tt>"change"</tt>
      event immediately, and a <tt>"sync"</tt> event after the server has acknowledged
      the successful change. Pass <tt>{wait: true}</tt> if you'd like to wait
      for the server before setting the new attributes on the model.
    </p>

    <p>
      In the following example, notice how our overridden version
      of <tt>Backbone.sync</tt> receives a <tt>"create"</tt> request
      the first time the model is saved and an <tt>"update"</tt>
      request the second time.
    </p>

<pre class="runnable">
Backbone.sync = function(method, model) {
  alert(method + ": " + JSON.stringify(model));
  model.id = 1;
};

var book = new Backbone.Model({
  title: "The Rough Riders",
  author: "Theodore Roosevelt"
});

book.save();

book.save({author: "Teddy"});
</pre>

    <p>
      <b>save</b> accepts <tt>success</tt> and <tt>error</tt> callbacks in the
      options hash, which are passed <tt>(model, response)</tt> as arguments.
      The <tt>error</tt> callback will also be invoked if the model has a
      <tt>validate</tt> method, and validation fails. If a server-side
      validation fails, return a non-<tt>200</tt> HTTP response code, along with
      an error response in text or JSON.
    </p>

<pre>
book.save("author", "F.D.R.", {error: function(){ ... }});
</pre>

    <p id="Model-destroy">
      <b class="header">destroy</b><code>model.destroy([options])</code>
      <br />
      Destroys the model on the server by delegating an HTTP <tt>DELETE</tt>
      request to <a href="#Sync">Backbone.sync</a>. Returns a
      <a href="http://api.jquery.com/jQuery.ajax/#jqXHR">jqXHR</a> object, or
      <tt>false</tt> if the model <a href="#Model-isNew">isNew</a>. Accepts
      <tt>success</tt> and <tt>error</tt> callbacks in the options hash.
      Triggers a <tt>"destroy"</tt> event on the model, which will bubble up
      through any collections that contain it, and a <tt>"sync"</tt> event, after
      the server has successfully acknowledged the model's deletion. Pass
      <tt>{wait: true}</tt> if you'd like to wait for the server to respond
      before removing the model from the collection.
    </p>

<pre>
book.destroy({success: function(model, response) {
  ...
}});
</pre>

    <p id="Model-validate">
      <b class="header">validate</b><code>model.validate(attributes)</code>
      <br />
      This method is left undefined, and you're encouraged to override it with
      your custom validation logic, if you have any that can be performed
      in JavaScript. <b>validate</b> is called before <tt>set</tt> and
      <tt>save</tt>, and is passed the model attributes updated with the values
      from <tt>set</tt> or <tt>save</tt>.
      If the attributes are valid, don't return anything from <b>validate</b>;
      if they are invalid, return an error of your choosing. It
      can be as simple as a string error message to be displayed, or a complete
      error object that describes the error programmatically. If <b>validate</b>
      returns an error, <tt>set</tt> and <tt>save</tt> will not continue, and the
      model attributes will not be modified.
      Failed validations trigger an <tt>"error"</tt> event.
    </p>

<pre class="runnable">
var Chapter = Backbone.Model.extend({
  validate: function(attrs) {
    if (attrs.end < attrs.start) {
      return "can't end before it starts";
    }
  }
});

var one = new Chapter({
  title : "Chapter One: The Beginning"
});

one.on("error", function(model, error) {
  alert(model.get("title") + " " + error);
});

one.set({
  start: 15,
  end:   10
});
</pre>

    <p>
      <tt>"error"</tt> events are useful for providing coarse-grained error
      messages at the model or collection level, but if you have a specific view
      that can better handle the error, you may override and suppress the event
      by passing an <tt>error</tt> callback directly:
    </p>

<pre>
account.set({access: "unlimited"}, {
  error: function(model, error) {
    alert(error);
  }
});
</pre>

    <p id="Model-isValid">
      <b class="header">isValid</b><code>model.isValid()</code>
      <br />
      Models may enter an invalid state if you make changes to them silently
      ... useful when dealing with form input. Call <tt>model.isValid()</tt>
      to check if the model is currently in a valid state, according to your
      <tt>validate</tt> function.
    </p>

    <p id="Model-url">
      <b class="header">url</b><code>model.url()</code>
      <br />
      Returns the relative URL where the model's resource would be located on
      the server. If your models are located somewhere else, override this method
      with the correct logic. Generates URLs of the form: <tt>"/[collection.url]/[id]"</tt>
      by default, but you may override by specifying an explicit <tt>urlRoot</tt>
      if the model's collection shouldn't be taken into account.
    </p>

    <p>
      Delegates to <a href="#Collection-url">Collection#url</a> to generate the
      URL, so make sure that you have it defined, or a <a href="#Model-urlRoot">urlRoot</a>
      property, if all models of this class share a common root URL.
      A model with an id of <tt>101</tt>, stored in a
      <a href="#Collection">Backbone.Collection</a> with a <tt>url</tt> of <tt>"/documents/7/notes"</tt>,
      would have this URL: <tt>"/documents/7/notes/101"</tt>
    </p>

    <p id="Model-urlRoot">
      <b class="header">urlRoot</b><code>model.urlRoot or model.urlRoot()</code>
      <br />
      Specify a <tt>urlRoot</tt> if you're using a model <i>outside</i> of a collection,
      to enable the default <a href="#Model-url">url</a> function to generate
      URLs based on the model id. <tt>"/[urlRoot]/id"</tt><br />
      Normally, you won't need to define this.
      Note that <tt>urlRoot</tt> may also be a function.
    </p>

<pre class="runnable">
var Book = Backbone.Model.extend({urlRoot : '/books'});

var solaris = new Book({id: "1083-lem-solaris"});

alert(solaris.url());
</pre>

    <p id="Model-parse">
      <b class="header">parse</b><code>model.parse(response)</code>
      <br />
      <b>parse</b> is called whenever a model's data is returned by the
      server, in <a href="#Model-fetch">fetch</a>, and <a href="#Model-save">save</a>.
      The function is passed the raw <tt>response</tt> object, and should return
      the attributes hash to be <a href="#Model-set">set</a> on the model. The
      default implementation is a no-op, simply passing through the JSON response.
      Override this if you need to work with a preexisting API, or better namespace
      your responses.
    </p>

    <p>
      If you're working with a Rails backend that has a version prior to 3.1,
      you'll notice that its default <tt>to_json</tt> implementation includes
      a model's attributes under a namespace. To disable this behavior for
      seamless Backbone integration, set:
    </p>

<pre>
ActiveRecord::Base.include_root_in_json = false
</pre>

    <p id="Model-clone">
      <b class="header">clone</b><code>model.clone()</code>
      <br />
      Returns a new instance of the model with identical attributes.
    </p>

    <p id="Model-isNew">
      <b class="header">isNew</b><code>model.isNew()</code>
      <br />
      Has this model been saved to the server yet? If the model does not yet have
      an <tt>id</tt>, it is considered to be new.
    </p>

    <p id="Model-change">
      <b class="header">change</b><code>model.change()</code>
      <br />
      Manually trigger the <tt>"change"</tt> event and a <tt>"change:attribute"</tt>
      event for each attribute that has changed. If you've been passing
      <tt>{silent: true}</tt> to the <a href="#Model-set">set</a> function in order to
      aggregate rapid changes to a model, you'll want to call <tt>model.change()</tt>
      when you're all finished.
    </p>

    <p id="Model-hasChanged">
      <b class="header">hasChanged</b><code>model.hasChanged([attribute])</code>
      <br />
      Has the model changed since the last <tt>"change"</tt> event? If an <b>attribute</b>
      is passed, returns <tt>true</tt> if that specific attribute has changed.
    </p>

    <p class="warning">
      Note that this method, and the following change-related ones,
      are only useful during the course of a <tt>"change"</tt> event.
    </p>

<pre>
book.on("change", function() {
  if (book.hasChanged("title")) {
    ...
  }
});
</pre>

    <p id="Model-changedAttributes">
      <b class="header">changedAttributes</b><code>model.changedAttributes([attributes])</code>
      <br />
      Retrieve a hash of only the model's attributes that have changed. Optionally,
      an external <b>attributes</b> hash can be passed in, returning
      the attributes in that hash which differ from the model. This can be used
      to figure out which portions of a view should be updated, or what calls
      need to be made to sync the changes to the server.
    </p>

    <p id="Model-previous">
      <b class="header">previous</b><code>model.previous(attribute)</code>
      <br />
      During a <tt>"change"</tt> event, this method can be used to get the
      previous value of a changed attribute.
    </p>

<pre class="runnable">
var bill = new Backbone.Model({
  name: "Bill Smith"
});

bill.on("change:name", function(model, name) {
  alert("Changed name from " + bill.previous("name") + " to " + name);
});

bill.set({name : "Bill Jones"});
</pre>

    <p id="Model-previousAttributes">
      <b class="header">previousAttributes</b><code>model.previousAttributes()</code>
      <br />
      Return a copy of the model's previous attributes. Useful for getting a
      diff between versions of a model, or getting back to a valid state after
      an error occurs.
    </p>

    <h2 id="Collection">Backbone.Collection</h2>

    <p>
      Collections are ordered sets of models. You can bind <tt>"change"</tt> events
      to be notified when any model in the collection has been modified,
      listen for <tt>"add"</tt> and <tt>"remove"</tt> events, <tt>fetch</tt>
      the collection from the server, and use a full suite of
      <a href="#Collection-Underscore-Methods">Underscore.js methods</a>.
    </p>

    <p>
      Any event that is triggered on a model in a collection will also be
      triggered on the collection directly, for convenience.
      This allows you to listen for changes to specific attributes in any
      model in a collection, for example:
      <tt>Documents.on("change:selected", ...)</tt>
    </p>

    <p id="Collection-extend">
      <b class="header">extend</b><code>Backbone.Collection.extend(properties, [classProperties])</code>
      <br />
      To create a <b>Collection</b> class of your own, extend <b>Backbone.Collection</b>,
      providing instance <b>properties</b>, as well as optional <b>classProperties</b> to be attached
      directly to the collection's constructor function.
    </p>

    <p id="Collection-model">
      <b class="header">model</b><code>collection.model</code>
      <br />
      Override this property to specify the model class that the collection
      contains. If defined, you can pass raw attributes objects (and arrays) to
      <a href="#Collection-add">add</a>, <a href="#Collection-create">create</a>,
      and <a href="#Collection-reset">reset</a>, and the attributes will be
      converted into a model of the proper type.
    </p>

<pre>
var Library = Backbone.Collection.extend({
  model: Book
});
</pre>

    <p id="Collection-constructor">
      <b class="header">constructor / initialize</b><code>new Collection([models], [options])</code>
      <br />
      When creating a Collection, you may choose to pass in the initial array
      of <b>models</b>.  The collection's <a href="#Collection-comparator">comparator</a>
      may be included as an option. Passing <tt>false</tt> as the
      comparator option will prevent sorting. If you define an
      <b>initialize</b> function, it will be invoked when the collection is
      created.
    </p>

<pre>
var tabs = new TabSet([tab1, tab2, tab3]);
</pre>

    <p id="Collection-models">
      <b class="header">models</b><code>collection.models</code>
      <br />
      Raw access to the JavaScript array of models inside of the collection. Usually you'll
      want to use <tt>get</tt>, <tt>at</tt>, or the <b>Underscore methods</b>
      to access model objects, but occasionally a direct reference to the array
      is desired.
    </p>

    <p id="Collection-toJSON">
      <b class="header">toJSON</b><code>collection.toJSON()</code>
      <br />
      Return an array containing the attributes hash of each model in the
      collection. This can be used to serialize and persist the
      collection as a whole. The name of this method is a bit confusing, because
      it conforms to
      <a href="https://developer.mozilla.org/en/JSON#toJSON()_method">JavaScript's JSON API</a>.
    </p>

<pre class="runnable">
var collection = new Backbone.Collection([
  {name: "Tim", age: 5},
  {name: "Ida", age: 26},
  {name: "Rob", age: 55}
]);

alert(JSON.stringify(collection));
</pre>

    <p id="Collection-sync">
      <b class="header">sync</b><code>collection.sync(method, collection, [options])</code>
      <br />
      Uses <a href="#Sync">Backbone.sync</a> to persist the state of a
      collection to the server.  Can be overridden for custom behavior.
    </p>

    <p id="Collection-Underscore-Methods">
      <b class="header">Underscore Methods (28)</b>
      <br />
      Backbone proxies to <b>Underscore.js</b> to provide 28 iteration functions
      on <b>Backbone.Collection</b>. They aren't all documented here, but
      you can take a look at the Underscore documentation for the full details&hellip;
    </p>

    <ul class="small">
      <li><a href="http://underscorejs.org/#each">forEach (each)</a></li>
      <li><a href="http://underscorejs.org/#map">map (collect)</a></li>
      <li><a href="http://underscorejs.org/#reduce">reduce (foldl, inject)</a></li>
      <li><a href="http://underscorejs.org/#reduceRight">reduceRight (foldr)</a></li>
      <li><a href="http://underscorejs.org/#find">find (detect)</a></li>
      <li><a href="http://underscorejs.org/#filter">filter (select)</a></li>
      <li><a href="http://underscorejs.org/#reject">reject</a></li>
      <li><a href="http://underscorejs.org/#all">every (all)</a></li>
      <li><a href="http://underscorejs.org/#any">some (any)</a></li>
      <li><a href="http://underscorejs.org/#include">include (contains)</a></li>
      <li><a href="http://underscorejs.org/#invoke">invoke</a></li>
      <li><a href="http://underscorejs.org/#max">max</a></li>
      <li><a href="http://underscorejs.org/#min">min</a></li>
      <li><a href="http://underscorejs.org/#sortBy">sortBy</a></li>
      <li><a href="http://underscorejs.org/#groupBy">groupBy</a></li>
      <li><a href="http://underscorejs.org/#sortedIndex">sortedIndex</a></li>
      <li><a href="http://underscorejs.org/#shuffle">shuffle</a></li>
      <li><a href="http://underscorejs.org/#toArray">toArray</a></li>
      <li><a href="http://underscorejs.org/#size">size</a></li>
      <li><a href="http://underscorejs.org/#first">first (head, take)</a></li>
      <li><a href="http://underscorejs.org/#initial">initial</a></li>
      <li><a href="http://underscorejs.org/#rest">rest (tail)</a></li>
      <li><a href="http://underscorejs.org/#last">last</a></li>
      <li><a href="http://underscorejs.org/#without">without</a></li>
      <li><a href="http://underscorejs.org/#indexOf">indexOf</a></li>
      <li><a href="http://underscorejs.org/#lastIndexOf">lastIndexOf</a></li>
      <li><a href="http://underscorejs.org/#isEmpty">isEmpty</a></li>
      <li><a href="http://underscorejs.org/#chain">chain</a></li>
    </ul>

<pre>
Books.each(function(book) {
  book.publish();
});

var titles = Books.map(function(book) {
  return book.get("title");
});

var publishedBooks = Books.filter(function(book) {
  return book.get("published") === true;
});

var alphabetical = Books.sortBy(function(book) {
  return book.author.get("name").toLowerCase();
});
</pre>

    <p id="Collection-add">
      <b class="header">add</b><code>collection.add(models, [options])</code>
      <br />
      Add a model (or an array of models) to the collection. Fires an <tt>"add"</tt>
      event, which you can pass <tt>{silent: true}</tt> to suppress. If a
      <a href="#Collection-model">model</a> property is defined, you may also pass
      raw attributes objects, and have them be vivified as instances of the model.
      Pass <tt>{at: index}</tt> to splice the model into the collection at the
      specified <tt>index</tt>. Likewise, if you're a callback listening to a
      collection's <tt>"add"</tt> event, <tt>options.index</tt> will tell you the
      index at which the model is being added to the collection.
    </p>

<pre class="runnable">
var ships = new Backbone.Collection;

ships.on("add", function(ship) {
  alert("Ahoy " + ship.get("name") + "!");
});

ships.add([
  {name: "Flying Dutchman"},
  {name: "Black Pearl"}
]);
</pre>

    <p id="Collection-remove">
      <b class="header">remove</b><code>collection.remove(models, [options])</code>
      <br />
      Remove a model (or an array of models) from the collection. Fires a
      <tt>"remove"</tt> event, which you can use <tt>silent</tt>
      to suppress. If you're a callback listening to the <tt>"remove"</tt> event,
      the index at which the model is being removed from the collection is available
      as <tt>options.index</tt>.
    </p>

    <p id="Collection-get">
      <b class="header">get</b><code>collection.get(id)</code>
      <br />
      Get a model from a collection, specified by <b>id</b>.
    </p>

<pre>
var book = Library.get(110);
</pre>

    <p id="Collection-getByCid">
      <b class="header">getByCid</b><code>collection.getByCid(cid)</code>
      <br />
      Get a model from a collection, specified by client id. The client id
      is the <tt>.cid</tt> property of the model, automatically assigned whenever
      a model is created. Useful for models which have not yet been saved to
      the server, and do not yet have true ids.
    </p>

    <p id="Collection-at">
      <b class="header">at</b><code>collection.at(index)</code>
      <br />
      Get a model from a collection, specified by index. Useful if your collection
      is sorted, and if your collection isn't sorted, <b>at</b> will still
      retrieve models in insertion order.
    </p>

    <p id="Collection-push">
      <b class="header">push</b><code>collection.push(model, [options])</code>
      <br />
      Add a model at the end of a collection. Takes the same options as
      <a href="#Collection-add">add</a>.
    </p>

    <p id="Collection-pop">
      <b class="header">pop</b><code>collection.pop([options])</code>
      <br />
      Remove and return the last model from a collection. Takes the same options as
      <a href="#Collection-remove">remove</a>.
    </p>

    <p id="Collection-unshift">
      <b class="header">unshift</b><code>collection.unshift(model, [options])</code>
      <br />
      Add a model at the beginning of a collection. Takes the same options as
      <a href="#Collection-add">add</a>.
    </p>

    <p id="Collection-shift">
      <b class="header">shift</b><code>collection.shift([options])</code>
      <br />
      Remove and return the first model from a collection. Takes the same options as
      <a href="#Collection-remove">remove</a>.
    </p>

    <p id="Collection-length">
      <b class="header">length</b><code>collection.length</code>
      <br />
      Like an array, a Collection maintains a <tt>length</tt> property, counting
      the number of models it contains.
    </p>

    <p id="Collection-comparator">
      <b class="header">comparator</b><code>collection.comparator</code>
      <br />
      By default there is no <b>comparator</b> for a collection.
      If you define a comparator, it will be used to maintain
      the collection in sorted order. This means that as models are added,
      they are inserted at the correct index in <tt>collection.models</tt>.
      A comparator can be defined as a
      <a href="http://underscorejs.org/#sortBy">sortBy</a>
      (pass a function that takes a single argument),
      as a
      <a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/sort">sort</a>
      (pass a comparator function that expects two arguments),
      or as a string indicating the attribute to sort by.
    </p>

    <p>
      "sortBy" comparator functions take a model and return a numeric or string
      value by which the model should be ordered relative to others.
      "sort" comparator functions take two models, and return <tt>-1</tt> if
      the first model should come before the second, <tt>0</tt> if they are of
      the same rank and <tt>1</tt> if the first model should come after.
    </p>

    <p>
      Note how even though all of the chapters in this example are added backwards,
      they come out in the proper order:
    </p>

<pre class="runnable">
var Chapter  = Backbone.Model;
var chapters = new Backbone.Collection;

chapters.comparator = function(chapter) {
  return chapter.get("page");
};

chapters.add(new Chapter({page: 9, title: "The End"}));
chapters.add(new Chapter({page: 5, title: "The Middle"}));
chapters.add(new Chapter({page: 1, title: "The Beginning"}));

alert(chapters.pluck('title'));
</pre>

    <p class="warning">
      Collections with a comparator will not automatically re-sort if you
      later change model attributes, so you may wish to call
      <tt>sort</tt> after changing model attributes that would affect the order.
    </p>

    <p id="Collection-sort">
      <b class="header">sort</b><code>collection.sort([options])</code>
      <br />
      Force a collection to re-sort itself. You don't need to call this under
      normal circumstances, as a collection with a <a href="#Collection-comparator">comparator</a>
      will sort itself whenever a model is added. Calling <b>sort</b>
      triggers the collection's <tt>"reset"</tt> event, unless silenced by passing
      <tt>{silent: true}</tt>
    </p>

    <p id="Collection-pluck">
      <b class="header">pluck</b><code>collection.pluck(attribute)</code>
      <br />
      Pluck an attribute from each model in the collection. Equivalent to calling
      <tt>map</tt>, and returning a single attribute from the iterator.
    </p>

<pre class="runnable">
var stooges = new Backbone.Collection([
  {name: "Curly"},
  {name: "Larry"},
  {name: "Moe"}
]);

var names = stooges.pluck("name");

alert(JSON.stringify(names));
</pre>

    <p id="Collection-where">
      <b class="header">where</b><code>collection.where(attributes)</code>
      <br />
      Return an array of all the models in a collection that match the
      passed <b>attributes</b>. Useful for simple cases of <tt>filter</tt>.
    </p>

<pre class="runnable">
var friends = new Backbone.Collection([
  {name: "Athos",      job: "Musketeer"},
  {name: "Porthos",    job: "Musketeer"},
  {name: "Aramis",     job: "Musketeer"},
  {name: "d'Artagnan", job: "Guard"},
]);

var musketeers = friends.where({job: "Musketeer"});

alert(musketeers.length);
</pre>

    <p id="Collection-url">
      <b class="header">url</b><code>collection.url or collection.url()</code>
      <br />
      Set the <b>url</b> property (or function) on a collection to reference
      its location on the server. Models within the collection will use <b>url</b>
      to construct URLs of their own.
    </p>

<pre>
var Notes = Backbone.Collection.extend({
  url: '/notes'
});

// Or, something more sophisticated:

var Notes = Backbone.Collection.extend({
  url: function() {
    return this.document.url() + '/notes';
  }
});
</pre>

    <p id="Collection-parse">
      <b class="header">parse</b><code>collection.parse(response)</code>
      <br />
      <b>parse</b> is called by Backbone whenever a collection's models are
      returned by the server, in <a href="#Collection-fetch">fetch</a>.
      The function is passed the raw <tt>response</tt> object, and should return
      the array of model attributes to be <a href="#Collection-add">added</a>
      to the collection. The default implementation is a no-op, simply passing
      through the JSON response. Override this if you need to work with a
      preexisting API, or better namespace your responses. Note that afterwards,
      if your model class already has a <tt>parse</tt> function, it will be
      run against each fetched model.
    </p>

<pre>
var Tweets = Backbone.Collection.extend({
  // The Twitter Search API returns tweets under "results".
  parse: function(response) {
    return response.results;
  }
});
</pre>

    <p id="Collection-clone">
      <b class="header">clone</b><code>collection.clone()</code>
      <br />
      Returns a new instance of the collection with an identical list of models.
    </p>

    <p id="Collection-fetch">
      <b class="header">fetch</b><code>collection.fetch([options])</code>
      <br />
      Fetch the default set of models for this collection from the server,
      resetting the collection when they arrive. The <b>options</b> hash takes
      <tt>success</tt> and <tt>error</tt>
      callbacks which will be passed <tt>(collection, response)</tt> as arguments.
      When the model data returns from the server, the collection will
      <a href="#Collection-reset">reset</a>.
      Delegates to <a href="#Sync">Backbone.sync</a>
      under the covers for custom persistence strategies and returns a
      <a href="http://api.jquery.com/jQuery.ajax/#jqXHR">jqXHR</a>.
      The server handler for <b>fetch</b> requests should return a JSON array of
      models.
    </p>

<pre class="runnable">
Backbone.sync = function(method, model) {
  alert(method + ": " + model.url);
};

var Accounts = new Backbone.Collection;
Accounts.url = '/accounts';

Accounts.fetch();
</pre>

    <p>
      If you'd like to add the incoming models to the current collection, instead
      of replacing the collection's contents, pass <tt>{add: true}</tt> as an
      option to <b>fetch</b>.
    </p>

    <p>
      <b>jQuery.ajax</b> options can also be passed directly as <b>fetch</b> options,
      so to fetch a specific page of a paginated collection:
      <tt>Documents.fetch({data: {page: 3}})</tt>
    </p>

    <p>
      Note that <b>fetch</b> should not be used to populate collections on
      page load &mdash; all models needed at load time should already be
      <a href="#FAQ-bootstrap">bootstrapped</a> in to place. <b>fetch</b> is
      intended for lazily-loading models for interfaces that are not needed
      immediately: for example, documents with collections of notes that may be
      toggled open and closed.
    </p>

    <p id="Collection-reset">
      <b class="header">reset</b><code>collection.reset(models, [options])</code>
      <br />
      Adding and removing models one at a time is all well and good, but sometimes
      you have so many models to change that you'd rather just update the collection
      in bulk. Use <b>reset</b> to replace a collection with a new list
      of models (or attribute hashes), triggering a single <tt>"reset"</tt> event
      at the end. Pass <tt>{silent: true}</tt> to suppress the <tt>"reset"</tt> event.
      Using reset with no arguments is useful as a way to empty the collection.
    </p>

    <p>
      Here's an example using <b>reset</b> to bootstrap a collection during initial page load,
      in a Rails application.
    </p>

<pre>
&lt;script&gt;
  var Accounts = new Backbone.Collection;
  Accounts.reset(&lt;%= @accounts.to_json %&gt;);
&lt;/script&gt;
</pre>

    <p>
      Calling <tt>collection.reset()</tt> without passing any models as arguments
      will empty the entire collection.
    </p>

    <p id="Collection-create">
      <b class="header">create</b><code>collection.create(attributes, [options])</code>
      <br />
      Convenience to create a new instance of a model within a collection.
      Equivalent to instantiating a model with a hash of attributes,
      saving the model to the server, and adding the model to the set after being
      successfully created. Returns
      the model, or <tt>false</tt> if a validation error prevented the
      model from being created. In order for this to work, you should set the
      <a href="#Collection-model">model</a> property of the collection.
      The <b>create</b> method can accept either an attributes hash or an
      existing, unsaved model object.
    </p>

    <p>
      Creating a model will cause an immediate <tt>"add"</tt> event to be
      triggered on the collection, as well as a <tt>"sync"</tt> event, once the
      model has been successfully created on the server. Pass <tt>{wait: true}</tt>
      if you'd like to wait for the server before adding the new model to the collection.
    </p>

<pre>
var Library = Backbone.Collection.extend({
  model: Book
});

var NYPL = new Library;

var othello = NYPL.create({
  title: "Othello",
  author: "William Shakespeare"
});
</pre>

    <h2 id="Router">Backbone.Router</h2>

    <p>
      Web applications often provide linkable, bookmarkable, shareable URLs for
      important locations in the app. Until recently, hash fragments
      (<tt>#page</tt>) were used to provide these permalinks, but with the
      arrival of the History API, it's now possible to use standard URLs (<tt>/page</tt>).
      <b>Backbone.Router</b> provides methods for routing client-side pages, and
      connecting them to actions and events. For browsers which don't yet support
      the History API, the Router handles graceful fallback and transparent
      translation to the fragment version of the URL.
    </p>

    <p>
      During page load, after your application has finished creating all of its routers,
      be sure to call <tt>Backbone.history.start()</tt>, or
      <tt>Backbone.history.start({pushState: true})</tt> to route the initial URL.
    </p>

    <p id="Router-extend">
      <b class="header">extend</b><code>Backbone.Router.extend(properties, [classProperties])</code>
      <br />
      Get started by creating a custom router class. Define actions that are
      triggered when certain URL fragments are
      matched, and provide a <a href="#Router-routes">routes</a> hash
      that pairs routes to actions. Note that you'll want to avoid using a
      leading slash in your route definitions:
    </p>

<pre>
var Workspace = Backbone.Router.extend({

  routes: {
    "help":                 "help",    // #help
    "search/:query":        "search",  // #search/kiwis
    "search/:query/p:page": "search"   // #search/kiwis/p7
  },

  help: function() {
    ...
  },

  search: function(query, page) {
    ...
  }

});
</pre>

    <p id="Router-routes">
      <b class="header">routes</b><code>router.routes</code>
      <br />
      The routes hash maps URLs with parameters to functions on your router,
      similar to the <a href="#View">View</a>'s <a href="#View-delegateEvents">events hash</a>.
      Routes can contain parameter parts, <tt>:param</tt>, which match a single URL
      component between slashes; and splat parts <tt>*splat</tt>, which can match
      any number of URL components.
    </p>

    <p>
      For example, a route of <tt>"search/:query/p:page"</tt> will match
      a fragment of <tt>#search/obama/p2</tt>, passing <tt>"obama"</tt>
      and <tt>"2"</tt> to the action. A route of <tt>"file/*path"</tt> will
      match <tt>#file/nested/folder/file.txt</tt>,
      passing <tt>"nested/folder/file.txt"</tt> to the action.
    </p>

    <p>
      When the visitor presses the back button, or enters a URL, and a particular
      route is matched, the name of the action will be fired as an
      <a href="#Events">event</a>, so that other objects can listen to the router,
      and be notified. In the following example, visiting <tt>#help/uploading</tt>
      will fire a <tt>route:help</tt> event from the router.
    </p>

<pre>
routes: {
  "help/:page":         "help",
  "download/*path":     "download",
  "folder/:name":       "openFolder",
  "folder/:name-:mode": "openFolder"
}
</pre>

<pre>
router.on("route:help", function(page) {
  ...
});
</pre>

    <p id="Router-constructor">
      <b class="header">constructor / initialize</b><code>new Router([options])</code>
      <br />
      When creating a new router, you may pass its
      <a href="#Router-routes">routes</a> hash directly as an option, if you
      choose. All <tt>options</tt> will also be passed to your <tt>initialize</tt>
      function, if defined.
    </p>

    <p id="Router-route">
      <b class="header">route</b><code>router.route(route, name, [callback])</code>
      <br />
      Manually create a route for the router, The <tt>route</tt> argument may
      be a <a href="#Router-routes">routing string</a> or regular expression.
      Each matching capture from the route or regular expression will be passed as
      an argument to the callback. The <tt>name</tt> argument will be triggered as
      a <tt>"route:name"</tt> event whenever the route is matched.  If the
      <tt>callback</tt> argument is omitted <tt>router[name]</tt> will be used
      instead.
    </p>

<pre>
initialize: function(options) {

  // Matches #page/10, passing "10"
  this.route("page/:number", "page", function(number){ ... });

  // Matches /117-a/b/c/open, passing "117-a/b/c" to this.open
  this.route(/^(.*?)\/open$/, "open");

},

open: function(id) { ... }
</pre>

    <p id="Router-navigate">
      <b class="header">navigate</b><code>router.navigate(fragment, [options])</code>
      <br />
      Whenever you reach a point in your application that you'd like to save
      as a URL, call <b>navigate</b> in order to update the URL.
      If you wish to also call the route function, set the <b>trigger</b>
      option to <tt>true</tt>.
      To update the URL without creating an entry in the browser's history,
      set the <b>replace</b> option to <tt>true</tt>.
    </p>

<pre>
openPage: function(pageNumber) {
  this.document.pages.at(pageNumber).open();
  this.navigate("page/" + pageNumber);
}

# Or ...

app.navigate("help/troubleshooting", {trigger: true});

# Or ...

app.navigate("help/troubleshooting", {trigger: true, replace: true});
</pre>

    <h2 id="History">Backbone.history</h2>

    <p>
      <b>History</b> serves as a global router (per frame) to handle <tt>hashchange</tt>
      events or <tt>pushState</tt>, match the appropriate route, and trigger callbacks. You shouldn't
      ever have to create one of these yourself &mdash; you should use the reference
      to <tt>Backbone.history</tt> that will be created for you automatically if you make use
      of <a href="#Router">Routers</a> with <a href="#Router-routes">routes</a>.
    </p>

    <p>
      <b>pushState</b> support exists on a purely opt-in basis in Backbone.
      Older browsers that don't support <tt>pushState</tt> will continue to use
      hash-based URL fragments, and if a hash URL is visited by a
      <tt>pushState</tt>-capable browser, it will be transparently upgraded to
      the true URL. Note that using real URLs requires your web server to be
      able to correctly render those pages, so back-end changes are required
      as well. For example, if you have a route of <tt>/documents/100</tt>,
      your web server must be able to serve that page, if the browser
      visits that URL directly. For full search-engine crawlability, it's best to
      have the server generate the complete HTML for the page ... but if it's a web
      application, just rendering the same content you would have for the root URL,
      and filling in the rest with Backbone Views and JavaScript works fine.
    </p>

    <p id="History-start">
      <b class="header">start</b><code>Backbone.history.start([options])</code>
      <br />
      When all of your <a href="#Router">Routers</a> have been created,
      and all of the routes are set up properly, call <tt>Backbone.history.start()</tt>
      to begin monitoring <tt>hashchange</tt> events, and dispatching routes.
    </p>

    <p>
      To indicate that you'd like to use HTML5 <tt>pushState</tt> support in
      your application, use <tt>Backbone.history.start({pushState: true})</tt>.
    </p>

    <p>
      If your application is not being served from the root url <tt>/</tt> of your
      domain, be sure to tell History where the root really is, as an option:
      <tt>Backbone.history.start({pushState: true, root: "/public/search/"})</tt>
    </p>

    <p>
      When called, if a route succeeds with a match for the current URL,
      <tt>Backbone.history.start()</tt> returns <tt>true</tt>. If no defined
      route matches the current URL, it returns <tt>false</tt>.
    </p>

    <p>
      If the server has already rendered the entire page, and you don't want the
      initial route to trigger when starting History, pass <tt>silent: true</tt>.
    </p>

    <p>
      Because hash-based history in Internet Explorer relies on an
      <tt>&lt;iframe&gt;</tt>, be sure to only call <tt>start()</tt> after the DOM
      is ready.
    </p>

<pre>
$(function(){
  new WorkspaceRouter();
  new HelpPaneRouter();
  Backbone.history.start({pushState: true});
});
</pre>

    <h2 id="Sync">Backbone.sync</h2>

    <p>
      <b>Backbone.sync</b> is the function that Backbone calls every time it
      attempts to read or save a model to the server. By default, it uses
      <tt>(jQuery/Zepto).ajax</tt> to make a RESTful JSON request and returns a
      <a href="http://api.jquery.com/jQuery.ajax/#jqXHR">jqXHR</a>. You can override
      it in order to use a different persistence strategy, such as WebSockets,
      XML transport, or Local Storage.
    </p>

    <p>
      The method signature of <b>Backbone.sync</b> is <tt>sync(method, model, [options])</tt>
    </p>

    <ul>
      <li><b>method</b> – the CRUD method (<tt>"create"</tt>, <tt>"read"</tt>, <tt>"update"</tt>, or <tt>"delete"</tt>)</li>
      <li><b>model</b> – the model to be saved (or collection to be read)</li>
      <li><b>options</b> – success and error callbacks, and all other jQuery request options</li>
    </ul>

    <p>
      With the default implementation, when <b>Backbone.sync</b> sends up a request to save
      a model, its attributes will be passed, serialized as JSON, and sent in the HTTP body
      with content-type <tt>application/json</tt>. When returning a JSON response,
      send down the attributes of the  model that have been changed by the server, and need
      to be updated on the client. When responding to a <tt>"read"</tt> request from a collection
      (<a href="#Collection#fetch">Collection#fetch</a>), send down an array
      of model attribute objects.
    </p>

    <p>
      The <b>sync</b> function may be overriden globally as <tt>Backbone.sync</tt>,
      or at a finer-grained level, by adding a <tt>sync</tt> function to a Backbone
      collection or to an individual model.
    </p>

    <p>
      The default <b>sync</b> handler maps CRUD to REST like so:
    </p>

    <ul>
      <li><b>create &rarr; POST &nbsp; </b><tt>/collection</tt></li>
      <li><b>read &rarr; GET &nbsp; </b><tt>/collection[/id]</tt></li>
      <li><b>update &rarr; PUT &nbsp; </b><tt>/collection/id</tt></li>
      <li><b>delete &rarr; DELETE &nbsp; </b><tt>/collection/id</tt></li>
    </ul>

    <p>
      As an example, a Rails handler responding to an <tt>"update"</tt> call from
      <tt>Backbone</tt> might look like this: <i>(In real code, never use
      </i><tt>update_attributes</tt><i> blindly, and always whitelist the attributes
      you allow to be changed.)</i>
    </p>

<pre>
def update
  account = Account.find params[:id]
  account.update_attributes params
  render :json => account
end
</pre>

    <p>
      One more tip for integrating Rails versions prior to 3.1 is to disable
      the default namespacing for <tt>to_json</tt> calls on models by setting
      <tt>ActiveRecord::Base.include_root_in_json = false</tt>
    </p>

    <p id="Sync-ajax">
      <b class="header">ajax</b><code>Backbone.ajax = function(settings){ ... };</code>
      <br />
      If you want to use a custom ajax method or your ajax method doesn't support the
      <a href="http://api.jquery.com/jQuery.ajax/">jQuery.ajax</a> api and you need to
      translate the options you can do so by setting <tt>Backbone.ajax</tt>.  The method
      you supply will be used instead of the default <tt>$.ajax</tt>.
    </p>

    <p id="Sync-emulateHTTP">
      <b class="header">emulateHTTP</b><code>Backbone.emulateHTTP = true</code>
      <br />
      If you want to work with a legacy web server that doesn't support Backbone's
      default REST/HTTP approach, you may choose to turn on <tt>Backbone.emulateHTTP</tt>.
      Setting this option will fake <tt>PUT</tt> and <tt>DELETE</tt> requests with
      a HTTP <tt>POST</tt>, setting the <tt>X-HTTP-Method-Override</tt> header
      with the true method. If <tt>emulateJSON</tt> is also on, the true method
      will be passed as an additional <tt>_method</tt> parameter.
    </p>

<pre>
Backbone.emulateHTTP = true;

model.save();  // POST to "/collection/id", with "_method=PUT" + header.
</pre>

    <p id="Sync-emulateJSON">
      <b class="header">emulateJSON</b><code>Backbone.emulateJSON = true</code>
      <br />
      If you're working with a legacy web server that can't handle requests
      encoded as <tt>application/json</tt>, setting <tt>Backbone.emulateJSON = true;</tt>
      will cause the JSON to be serialized under a <tt>model</tt> parameter, and
      the request to be made with a <tt>application/x-www-form-urlencoded</tt>
      mime type, as if from an HTML form.
    </p>

    <h2 id="View">Backbone.View</h2>

    <p>
      Backbone views are almost more convention than they are code &mdash; they
      don't determine anything about your HTML or CSS for you, and can be used
      with any JavaScript templating library.
      The general idea is to organize your interface into logical views,
      backed by models, each of which can be updated independently when the
      model changes, without having to redraw the page. Instead of digging into
      a JSON object, looking up an element in the DOM, and updating the HTML by hand,
      you can bind your view's <tt>render</tt> function to the model's <tt>"change"</tt>
      event &mdash; and now everywhere that
      model data is displayed in the UI, it is always immediately up to date.
    </p>

    <p id="View-extend">
      <b class="header">extend</b><code>Backbone.View.extend(properties, [classProperties])</code>
      <br />
      Get started with views by creating a custom view class. You'll want to
      override the <a href="#View-render">render</a> function, specify your
      declarative <a href="#View-delegateEvents">events</a>, and perhaps the
      <tt>tagName</tt>, <tt>className</tt>, or <tt>id</tt> of the View's root
      element.
    </p>

<pre>
var DocumentRow = Backbone.View.extend({

  tagName: "li",

  className: "document-row",

  events: {
    "click .icon":          "open",
    "click .button.edit":   "openEditDialog",
    "click .button.delete": "destroy"
  },

  render: function() {
    ...
  }

});
</pre>

    <p id="View-constructor">
      <b class="header">constructor / initialize</b><code>new View([options])</code>
      <br />
      When creating a new View, the options you pass are attached to the view
      as <tt>this.options</tt>, for future reference. There are several special
      options that, if passed, will be attached directly to the view:
      <tt>model</tt>, <tt>collection</tt>,
      <tt>el</tt>, <tt>id</tt>, <tt>className</tt>, <tt>tagName</tt> and <tt>attributes</tt>.
      If the view defines an <b>initialize</b> function, it will be called when
      the view is first created. If you'd like to create a view that references
      an element <i>already</i> in the DOM, pass in the element as an option:
      <tt>new View({el: existingElement})</tt>
    </p>

<pre>
var doc = Documents.first();

new DocumentRow({
  model: doc,
  id: "document-row-" + doc.id
});
</pre>

    <p id="View-el">
      <b class="header">el</b><code>view.el</code>
      <br />
      All views have a DOM element at all times (the <b>el</b> property),
      whether they've already been inserted into the page or not. In this
      fashion, views can be rendered at any time, and inserted into the DOM all
      at once, in order to get high-performance UI rendering with as few
      reflows and repaints as possible. <tt>this.el</tt> is created from the
      view's <tt>tagName</tt>, <tt>className</tt>, <tt>id</tt> and <tt>attributes</tt> properties,
      if specified. If not, <b>el</b> is an empty <tt>div</tt>.
    </p>

<pre class="runnable">
var ItemView = Backbone.View.extend({
  tagName: 'li'
});

var BodyView = Backbone.View.extend({
  el: 'body'
});

var item = new ItemView();
var body = new BodyView();

alert(item.el + ' ' + body.el);
</pre>

    <p id="View-$el">
      <b class="header">$el</b><code>view.$el</code>
      <br />
      A cached jQuery (or Zepto) object for the view's element. A handy
      reference instead of re-wrapping the DOM element all the time.
    </p>

<pre>
view.$el.show();

listView.$el.append(itemView.el);
</pre>

    <p id="View-setElement">
      <b class="header">setElement</b><code>view.setElement(element)</code>
      <br />
      If you'd like to apply a Backbone view to a different DOM element, use
      <b>setElement</b>, which will also create the cached <tt>$el</tt> reference
      and move the view's delegated events from the old element to the new one.
    </p>

    <p id="View-attributes">
      <b class="header">attributes</b><code>view.attributes</code>
      <br />
      A hash of attributes that will be set as HTML DOM element attributes on the
      view's <tt>el</tt> (id, class, data-properties, etc.), or a function that
      returns such a hash.
    </p>

    <p id="View-dollar">
      <b class="header">$ (jQuery or Zepto)</b><code>view.$(selector)</code>
      <br />
      If jQuery or Zepto is included on the page, each view has a
      <b>$</b> function that runs queries scoped within the view's element. If you use this
      scoped jQuery function, you don't have to use model ids as part of your query
      to pull out specific elements in a list, and can rely much more on HTML class
      attributes. It's equivalent to running: <tt>view.$el.find(selector)</tt>
    </p>

<pre>
ui.Chapter = Backbone.View.extend({
  serialize : function() {
    return {
      title: this.$(".title").text(),
      start: this.$(".start-page").text(),
      end:   this.$(".end-page").text()
    };
  }
});
</pre>

    <p id="View-render">
      <b class="header">render</b><code>view.render()</code>
      <br />
      The default implementation of <b>render</b> is a no-op. Override this
      function with your code that renders the view template from model data,
      and updates <tt>this.el</tt> with the new HTML. A good
      convention is to <tt>return this</tt> at the end of <b>render</b> to
      enable chained calls.
    </p>

<pre>
var Bookmark = Backbone.View.extend({
  template: _.template(…),
  render: function() {
    this.$el.html(this.template(this.model.toJSON()));
    return this;
  }
});
</pre>

    <p>
      Backbone is agnostic with respect to your preferred method of HTML templating.
      Your <b>render</b> function could even munge together an HTML string, or use
      <tt>document.createElement</tt> to generate a DOM tree. However, we suggest
      choosing a nice JavaScript templating library.
      <a href="http://github.com/janl/mustache.js">Mustache.js</a>,
      <a href="http://github.com/creationix/haml-js">Haml-js</a>, and
      <a href="http://github.com/sstephenson/eco">Eco</a> are all fine alternatives.
      Because <a href="http://underscorejs.org/">Underscore.js</a> is already on the page,
      <a href="http://underscorejs.org/#template">_.template</a>
      is available, and is an excellent choice if you prefer simple
      interpolated-JavaScript style templates.
    </p>

    <p>
      Whatever templating strategy you end up with, it's nice if you <i>never</i>
      have to put strings of HTML in your JavaScript. At DocumentCloud, we
      use <a href="http://documentcloud.github.com/jammit/">Jammit</a> in order
      to package up JavaScript templates stored in <tt>/app/views</tt> as part
      of our main <tt>core.js</tt> asset package.
    </p>

    <p id="View-remove">
      <b class="header">remove</b><code>view.remove()</code>
      <br />
      <a href="#View-dispose">Dispose</a> of the view before removing it from
      the DOM via <tt>view.$el.remove()</tt>.
    </p>

    <p id="View-dispose">
      <b class="header">dispose</b><code>view.dispose()</code>
      <br />
      Clean up any references to the view in order to prevent unwanted latent
      effects and memory leaks.
    </p>

    <p id="View-make">
      <b class="header">make</b><code>view.make(tagName, [attributes], [content])</code>
      <br />
      Convenience function for creating a DOM element of the given type (<b>tagName</b>),
      with optional attributes and HTML content. Used internally to create the
      initial <tt>view.el</tt>.
    </p>

<pre class="runnable">
var view = new Backbone.View;

var el = view.make("b", {"class": "bold"}, "Bold! ");

$("#make-demo").append(el);
</pre>

<div id="make-demo"></div>

    <p id="View-delegateEvents">
      <b class="header">delegateEvents</b><code>delegateEvents([events])</code>
      <br />
      Uses jQuery's <tt>delegate</tt> function to provide declarative callbacks
      for DOM events within a view.
      If an <b>events</b> hash is not passed directly, uses <tt>this.events</tt>
      as the source. Events are written in the format <tt>{"event selector": "callback"}</tt>.
      The callback may be either the name of a method on the view, or a direct
      function body.
      Omitting the <tt>selector</tt> causes the event to be bound to the view's
      root element (<tt>this.el</tt>). By default, <tt>delegateEvents</tt> is called
      within the View's constructor for you, so if you have a simple <tt>events</tt>
      hash, all of your DOM events will always already be connected, and you will
      never have to call this function yourself.
    </p>

    <p>
      The <tt>events</tt> property may also be defined as a function that returns
      an <b>events</b> hash, to make it easier to programmatically define your
      events, as well as inherit them from parent views.
    </p>

    <p>
      Using <b>delegateEvents</b> provides a number of advantages over manually
      using jQuery to bind events to child elements during <a href="#View-render">render</a>. All attached
      callbacks are bound to the view before being handed off to jQuery, so when
      the callbacks are invoked, <tt>this</tt> continues to refer to the view object. When
      <b>delegateEvents</b> is run again, perhaps with a different <tt>events</tt>
      hash, all callbacks are removed and delegated afresh &mdash; useful for
      views which need to behave differently when in different modes.
    </p>

    <p>
      A view that displays a document in a search result might look
      something like this:
    </p>

<pre>
var DocumentView = Backbone.View.extend({

  events: {
    "dblclick"                : "open",
    "click .icon.doc"         : "select",
    "contextmenu .icon.doc"   : "showMenu",
    "click .show_notes"       : "toggleNotes",
    "click .title .lock"      : "editAccessLevel",
    "mouseover .title .date"  : "showTooltip"
  },

  render: function() {
    this.$el.html(this.template(this.model.toJSON()));
    return this;
  },

  open: function() {
    window.open(this.model.get("viewer_url"));
  },

  select: function() {
    this.model.set({selected: true});
  },

  ...

});
</pre>

    <p id="View-undelegateEvents">
      <b class="header">undelegateEvents</b><code>undelegateEvents()</code>
      <br />
      Removes all of the view's delegated events. Useful if you want to disable
      or remove a view from the DOM temporarily.
    </p>

    <h2 id="Utility">Utility</h2>

    <p id="Utility-Backbone-noConflict">
      <b class="header">Backbone.noConflict</b><code>var backbone = Backbone.noConflict();</code>
      <br />
      Returns the <tt>Backbone</tt> object back to its original value. You can
      use the return value of <tt>Backbone.noConflict()</tt> to keep a local
      reference to Backbone. Useful for embedding Backbone on third-party
      websites, where you don't want to clobber the existing Backbone.
    </p>

<pre>
var localBackbone = Backbone.noConflict();
var model = localBackbone.Model.extend(...);
</pre>

    <p id="Utility-Backbone-$">
      <b class="header">Backbone.$</b><code>Backbone.$ = $;</code>
      <br />
      If you have multiple copies of <tt>jQuery</tt> on the page, or simply want
      to tell Backbone to use a particular object as its DOM / Ajax library,
      this is the property for you.
    </p>

    <h2 id="examples">Examples</h2>

    <p>
      The list of examples that follows, while long, is not exhaustive. If you've
      worked on an app that uses Backbone, please add it to the
      <a href="https://github.com/documentcloud/backbone/wiki/Projects-and-Companies-using-Backbone">wiki page of Backbone apps</a>.
    </p>

    <p id="examples-todos">
      <a href="http://jgn.me/">Jérôme Gravel-Niquet</a> has contributed a
      <a href="examples/todos/index.html">Todo List application</a>
      that is bundled in the repository as Backbone example. If you're wondering
      where to get started with Backbone in general, take a moment to
      <a href="docs/todos.html">read through the annotated source</a>. The app uses a
      <a href="docs/backbone-localstorage.html">LocalStorage adapter</a>
      to transparently save all of your todos within your browser, instead of
      sending them to a server. Jérôme also has a version hosted at
      <a href="http://localtodos.com/">localtodos.com</a> that uses a
      <a href="http://github.com/jeromegn/backbone-mootools">MooTools-backed version of Backbone</a>
      instead of jQuery.
    </p>

    <div style="text-align: center;">
      <a href="examples/todos/index.html">
        <img width="400" height="427" data-original="docs/images/todos.png" alt="Todos" class="example_image" />
      </a>
    </div>

    <h2 id="examples-documentcloud">DocumentCloud</h2>

    <p>
      The <a href="http://www.documentcloud.org/public/#search/">DocumentCloud workspace</a>
      is built on Backbone.js, with <i>Documents</i>, <i>Projects</i>,
      <i>Notes</i>, and <i>Accounts</i> all as Backbone models and collections.
      If you're interested in history &mdash; both Underscore.js and Backbone.js
      were originally extracted from the DocumentCloud codebase, and packaged
      into standalone JS libraries.
    </p>

    <div style="text-align: center;">
      <a href="http://www.documentcloud.org/public/#search/">
        <img width="550" height="453" data-original="docs/images/dc-workspace.png" alt="DocumentCloud Workspace" class="example_image" />
      </a>
    </div>

    <h2 id="examples-rdio">Rdio</h2>

    <p>
      <a href="http://rdio.com/new">New Rdio</a> was developed from the ground
      up with a component based framework based on Backbone.js. Every component
      on the screen is dynamically loaded and rendered, with data provided by the
      <a href="http://developer.rdio.com/">Rdio API</a>. When changes are pushed,
      every component can update itself without reloading the page or interrupting
      the user's music. All of this relies on Backbone's views and models,
      and all URL routing is handled by Backbone's Router. When data changes are
      signaled in realtime, Backbone's Events notify the interested components
      in the data changes. Backbone forms the core of the new, dynamic, realtime
      Rdio web and <i>desktop</i> applications.
    </p>

    <div style="text-align: center;">
      <a href="http://rdio.com/new">
        <img width="550" height="344" data-original="docs/images/rdio.png" alt="Rdio" class="example_image" />
      </a>
    </div>

    <h2 id="examples-linkedin">LinkedIn Mobile</h2>

    <p>
      <a href="http://www.linkedin.com/">LinkedIn</a> used Backbone.js to create
      its <a href="http://www.linkedin.com/static?key=mobile">next-generation HTML5 mobile web app</a>.
      Backbone made it easy to keep the app modular, organized and extensible so
      that it was possible to program the complexities of LinkedIn's user experience.
      The app also uses <a href="http://zeptojs.com/">Zepto</a>,
      <a href="http://underscorejs.org/">Underscore.js</a>,
      <a href="http://sass-lang.com/">SASS</a>, <a href="http://cubiq.org/iscroll">iScroll</a>,
      HTML5 LocalStorage and Canvas. The tech team blogged about
      <a href="https://engineering.linkedin.com/mobile/linkedin-ipad-using-local-storage-snappy-mobile-apps">their experiences using LocalStorage</a>
      to improve mobile performance.
    </p>

    <div style="text-align: center;">
      <a href="http://www.linkedin.com/static?key=mobile">
        <img width="550" height"454" data-original="docs/images/linkedin-mobile.png" alt="LinkedIn Mobile" class="example_image" />
      </a>
    </div>

    <h2 id="examples-flow">Flow</h2>

    <p>
      <a href="http://www.metalabdesign.com/">MetaLab</a> used Backbone.js to create
      <a href="http://www.getflow.com/">Flow</a>, a task management app for teams. The
      workspace relies on Backbone.js to construct task views, activities, accounts,
      folders, projects, and tags. You can see the internals under <tt>window.Flow</tt>.
    </p>

    <div style="text-align: center;">
      <a href="http://www.getflow.com/">
        <img width="550" height="416" data-original="docs/images/flow.png" alt="Flow" class="example_image" />
      </a>
    </div>


  	<h2 id="examples-wordpress">WordPress.com</h2>

  	<p>
  		<a href="http://wordpress.com/">WordPress.com</a> is the software-as-a-service
  		version of <a href="http://wordpress.org">WordPress</a>. It uses Backbone.js
  		Models, Collections, and Views in its
  		<a href="http://en.blog.wordpress.com/2012/05/25/notifications-refreshed/">Notifications system</a>.  Backbone.js was selected
  		because it was easy to fit into the structure of the application, not the
  		other way around. <a href="http://automattic.com">Automattic</a>
  		(the company behind WordPress.com) is integrating Backbone.js into the
  		Stats tab and other features throughout the homepage.
  	</p>

    <div style="text-align: center;">
      <a href="http://wordpress.com/">
        <img width="550" height="387" data-original="docs/images/wpcom-notifications.png" alt="WordPress.com Notifications"
  	title="WordPress.com Notifications" class="example_image" />
      </a>
    </div>

    <h2 id="examples-foursquare">Foursquare</h2>

    <p>
      Foursquare is a fun little startup that helps you meet up with friends,
      discover new places, and save money. Backbone Models are heavily used in
      the core JavaScript API layer and Views power many popular features like
      the <a href="https://foursquare.com">homepage map</a> and
      <a href="https://foursquare.com/seriouseats/list/the-best-doughnuts-in-ny">lists</a>.
    </p>

    <div style="text-align: center;">
      <a href="http://foursquare.com">
        <img width="550" height="427" data-original="docs/images/foursquare.png" alt="Foursquare" class="example_image" />
      </a>
    </div>

    <h2 id="examples-wunderkit">Wunderkit</h2>

    <p>
      <a href="http://get.wunderkit.com/">Wunderkit</a> is a productivity and
      social collaboration platform. It
      uses Backbone.js as the foundation for the single-page application,
      which is backed by a RESTful Rails API.
      The freedom and agility that Backbone gives to developers
      made it possible to build Wunderkit in a very short time and
      extend it with custom features: a write-through cache using HTML5
      localStorage, and a view hierarchy extension to easily manage trees of
      sub-views. Aside from Backbone, Wunderkit also
      depends on <a href="http://jquery.com/">jQuery</a>, <a href="http://underscorejs.org/">Underscore</a>, <a href="http://requirejs.org/">Require.js</a>, <a href="http://lesscss.org/">LESS</a> and doT.js templates.
    </p>

    <div style="text-align: center;">
      <a href="http://get.wunderkit.com/">
        <img width="543" height="525" data-original="docs/images/wunderkit.png" alt="Wunderkit" class="example_image" />
      </a>
    </div>

    <h2 id="examples-disqus">Disqus</h2>

    <p>
      <a href="http://www.disqus.com">Disqus</a> chose Backbone.js to power the
      latest version of their commenting widget. Backbone&rsquo;s small
      footprint and easy extensibility made it the right choice for Disqus&rsquo;
      distributed web application, which is hosted entirely inside an iframe and
      served on thousands of large web properties, including IGN, Wired, CNN, MLB, and more.
    </p>

    <div style="text-align: center;">
      <a href="http://www.disqus.com">
        <img width="550" height="454" data-original="docs/images/disqus.png" alt="Disqus" class="example_image" />
      </a>
    </div>

    <h2 id="examples-khan-academy">Khan Academy</h2>

    <p>
      <a href="http://www.khanacademy.org">Khan Academy</a> is on a mission to
      provide a free world-class education to anyone anywhere. With thousands of
      videos, hundreds of JavaScript-driven exercises, and big plans for the
      future, Khan Academy uses Backbone to keep frontend code modular and organized.
      User profiles and goal setting are implemented with Backbone,
      <a href="http://jquery.com/">jQuery</a> and
      <a href="http://handlebarsjs.com/">Handlebars</a>, and most new feature
      work is being pushed to the client side, greatly increasing the quality of
      <a href="https://github.com/Khan/khan-api/">the API</a>.
    </p>

    <div style="text-align: center;">
      <a href="http://www.khanacademy.org">
        <img width="550" height="454" data-original="docs/images/khan-academy.png" alt="Khan Academy" class="example_image" />
      </a>
    </div>

    <h2 id="examples-do">Do</h2>

    <p>
      <a href="http://do.com">Do</a> is a social productivity app that makes it
      easy to work on tasks, track projects, and take notes with your team.
      The <a href="http://do.com">Do.com</a> web application was built from the
      ground up to work seamlessly on your smartphone, tablet and computer. The
      team used Backbone, <a href="http://coffeescript.org/">CoffeeScript</a> and <a href="http://handlebarsjs.com/">Handlebars</a> to build a full-featured
      app in record time and rolled their own extensions for complex navigation
      and model sync support.
    </p>

    <div style="text-align: center;">
      <a href="http://do.com">
        <img width="550" height="425" data-original="docs/images/do.png" alt="Do" class="example_image" />
      </a>
    </div>

    <h2 id="examples-pitchfork">Pitchfork</h2>

    <p>
      <a href="http://pitchfork.com/">Pitchfork</a> uses Backbone.js to power
      its site-wide audio player, <a href="http://pitchfork.com/tv/">Pitchfork.tv</a>,
      location routing, a write-thru page fragment cache, and more. Backbone.js
      (and <a href="http://underscorejs.org/">Underscore.js</a>) helps the team
      create clean and modular components,
      move very quickly, and focus on the site, not the spaghetti.
    </p>

    <div style="text-align: center;">
      <a href="http://pitchfork.com/">
        <img width="550" height="428" data-original="docs/images/pitchfork.png" alt="Pitchfork" class="example_image" />
      </a>
    </div>

    <h2 id="examples-spin">Spin</h2>

    <p>
      <a href="http://spin.com/">Spin</a> pulls in the
      <a href="http://www.spin.com/news">latest news stories</a> from
      their internal API onto their site using Backbone models and collections, and a
      custom <tt>sync</tt> method. Because the music should never stop playing,
      even as you click through to different "pages", Spin uses a Backbone router
      for navigation within the site.
    </p>

    <div style="text-align: center;">
      <a href="http://spin.com/">
        <img width="550" height="543" data-original="docs/images/spin.png" alt="Spin" class="example_image" />
      </a>
    </div>

    <h2 id="examples-walmart">Walmart Mobile</h2>

    <p>
      <a href="http://www.walmart.com/">Walmart</a> used Backbone.js to create the new version
      of <a href="http://mobile.walmart.com/r/phoenix">their mobile web application</a> and
      created two new frameworks in the process.
      <a href="http://walmartlabs.github.com/thorax/">Thorax</a> provides mixins, inheritable
      events, as well as model and collection view bindings that integrate directly with
      <a href="http://handlebarsjs.com/">Handlebars</a> templates.
      <a href="http://walmartlabs.github.com/lumbar/">Lumbar</a> allows the application to be
      split into modules which can be loaded on demand, and creates platform specific builds
      for the portions of the web application that are embedded in Walmart's native Android
      and iOS applications.
    </p>

    <div style="text-align: center;">
      <a href="http://mobile.walmart.com/r/phoenix">
        <img width="256" height="500" data-original="docs/images/walmart-mobile.png" alt="Walmart Mobile" class="example_image" />
      </a>
    </div>

    <h2 id="examples-groupon">Groupon Now!</h2>

    <p>
      <a href="http://www.groupon.com/now">Groupon Now!</a> helps you find
      local deals that you can buy and use right now. When first developing
      the product, the team decided it would be AJAX heavy with smooth transitions
      between sections instead of full refreshes, but still needed to be fully
      linkable and shareable. Despite never having used Backbone before, the
      learning curve was incredibly quick &mdash; a prototype was hacked out in an
      afternoon, and the team was able to ship the product in two weeks.
      Because the source is minimal and understandable, it was easy to
      add several Backbone extensions for Groupon Now!: changing the router
      to handle URLs with querystring parameters, and adding a simple
      in-memory store for caching repeated requests for the same data.
    </p>

    <div style="text-align: center;">
      <a href="http://www.groupon.com/now">
        <img width="550" height="466" data-original="docs/images/groupon.png" alt="Groupon Now!" class="example_image" />
      </a>
    </div>

    <h2 id="examples-basecamp">Basecamp Mobile</h2>

    <p>
      <a href="http://37signals.com/">37Signals</a> used Backbone.js to create
      <a href="http://basecamphq.com/mobile">Basecamp Mobile</a>, the mobile version
      of their popular project management software. You can access all your Basecamp
      projects, post new messages, and comment on milestones (all represented
      internally as Backbone.js models).
    </p>

    <div style="text-align: center;">
      <a href="http://basecamphq.com/mobile">
        <img width="530" height="350" data-original="docs/images/basecamp-mobile.png" alt="Basecamp Mobile" class="example_image" />
      </a>
    </div>

    <h2 id="examples-slavery-footprint">Slavery Footprint</h2>

    <p>
      <a href="http://slaveryfootprint.org/survey">Slavery Footprint</a>
      allows consumers to visualize how their consumption habits are
      connected to modern-day slavery and provides them with an opportunity
      to have a deeper conversation with the companies that manufacture the
      goods they purchased.
      Based in Oakland, California, the Slavery Footprint team works to engage
      individuals, groups, and businesses to build awareness for and create
      deployable action against forced labor, human trafficking, and modern-day
      slavery through online tools, as well as off-line community education and
      mobilization programs.
    </p>

    <div style="text-align: center;">
      <a href="http://slaveryfootprint.org/survey">
        <img width="550" height="394" data-original="docs/images/slavery-footprint.png" alt="Slavery Footprint" class="example_image" />
      </a>
    </div>

    <h2 id="examples-stripe">Stripe</h2>

    <p>
      <a href="https://stripe.com">Stripe</a> provides an API for accepting
      credit cards on the web. Stripe's
      <a href="https://manage.stripe.com">management interface</a> was recently
      rewritten from scratch in Coffeescript using Backbone.js as the primary
      framework, <a href="https://github.com/sstephenson/eco">Eco</a> for templates, <a href="http://sass-lang.com/">Sass</a> for stylesheets, and <a href="https://github.com/sstephenson/stitch">Stitch</a> to package
      everything together as <a href="http://commonjs.org/">CommonJS</a> modules. The new app uses
      <a href="https://stripe.com/docs/api">Stripe's API</a> directly for the
      majority of its actions; Backbone.js models made it simple to map
      client-side models to their corresponding RESTful resources.
    </p>

    <div style="text-align: center;">
      <a href="https://stripe.com">
        <img width="555" height="372" data-original="docs/images/stripe.png" alt="Stripe" class="example_image" />
      </a>
    </div>

    <h2 id="examples-airbnb">Airbnb</h2>

    <p>
      <a href="http://airbnb.com">Airbnb</a> uses Backbone in many of its products.
      It started with <a href="http://m.airbnb.com">Airbnb Mobile Web</a>
      (built in six weeks by a team of three) and has since grown to
      <a href="https://www.airbnb.com/wishlists/popular">Wish Lists</a>,
      <a href="http://www.airbnb.com/match">Match</a>,
      <a href="http://www.airbnb.com/s/">Search</a>, Communities, Payments, and
      Internal Tools.
    </p>

    <div style="text-align: center;">
      <a href="http://m.airbnb.com/">
        <img width="500" height="489" data-original="docs/images/airbnb.png" alt="Airbnb" class="example_image" />
      </a>
    </div>

    <h2 id="examples-diaspora">Diaspora</h2>

    <p>
      <a href="http://www.joindiaspora.com/">Diaspora</a> is a distributed social
      network, formed from a number of independently operated <i>pods</i>.
      You own your personal data, and control with whom you share.
      All of Diaspora is <a href="https://github.com/diaspora/diaspora">open-source</a>
      code, built with <a href="http://rubyonrails.org/">Rails</a> and Backbone.js.
    </p>

    <div style="text-align: center;">
      <a href="http://www.joindiaspora.com/">
        <img width="550" height="394" data-original="docs/images/diaspora.png" alt="Diaspora" class="example_image" />
      </a>
    </div>

    <h2 id="examples-soundcloud">SoundCloud Mobile</h2>

    <p>
      <a href="http://soundcloud.com">SoundCloud</a> is the leading sound sharing
      platform on the internet, and Backbone.js provides the foundation for
      <a href="http://m.soundcloud.com">SoundCloud Mobile</a>. The project uses
      the public SoundCloud <a href="http://soundcloud.com/developers">API</a>
      as a data source (channeled through a nginx proxy),
      <a href="http://api.jquery.com/category/plugins/templates/">jQuery templates</a>
      for the rendering, <a href="http://docs.jquery.com/Qunit">Qunit
      </a> and <a href="http://www.phantomjs.org/">PhantomJS</a> for
      the testing suite. The JS code, templates and CSS are built for the
      production deployment with various Node.js tools like
      <a href="https://github.com/dsimard/ready.js">ready.js</a>,
      <a href="https://github.com/mde/jake">Jake</a>,
      <a href="https://github.com/tmpvar/jsdom">jsdom</a>.
      The <b>Backbone.History</b> was modified to support the HTML5 <tt>history.pushState</tt>.
      <b>Backbone.sync</b> was extended with an additional SessionStorage based cache
      layer.
    </p>

    <div style="text-align: center;">
      <a href="http://m.soundcloud.com">
        <img width="266" height="500" data-original="docs/images/soundcloud.png" alt="SoundCloud" class="example_image" />
      </a>
    </div>

    <h2 id="examples-artsy">Art.sy</h2>

    <p>
      <a href="http://art.sy">Art.sy</a> is a place to discover art you'll
      love. Art.sy is built on Rails, using
      <a href="https://github.com/intridea/grape">Grape</a> to serve a robust
      <a href="http://art.sy/api">JSON API</a>. The main site is a single page
      app written in Coffeescript and uses Backbone to provide structure around
      this API. An admin panel and partner CMS have also been extracted into
      their own API-consuming Backbone projects.
    </p>

    <div style="text-align: center;">
      <a href="http://art.sy">
        <img width="550" height="550" data-original="docs/images/artsy.png" alt="Art.sy" class="example_image" />
      </a>
    </div>

    <h2 id="examples-pandora">Pandora</h2>

    <p>
      When <a href="http://www.pandora.com/newpandora">Pandora</a> redesigned
      their site in HTML5, they chose Backbone.js to help
      manage the user interface and interactions. For example, there's a model
      that represents the "currently playing track", and multiple views that
      automatically update when the current track changes. The station list is a
      collection, so that when stations are added or changed, the UI stays up to date.
    </p>

    <div style="text-align: center;">
      <a href="http://www.pandora.com/newpandora">
        <img width="476" height="359" data-original="docs/images/pandora.png" alt="Pandora" class="example_image" />
      </a>
    </div>

    <h2 id="examples-inkling">Inkling</h2>

    <p>
      <a href="http://inkling.com">Inkling</a> is a truly
      cross-platform way to publish interactive learning content.<br />
      <a href="https://www.inkling.com/read/">Inkling for Web</a> uses Backbone.js
      to make hundreds of complex books &mdash; from textbooks to travel guides &mdash; more
      engaging on the web. Beyond your average EPUB eReader, Inkling supports
      WebGL-enabled 3D graphics, interactive assessments, seamless social sharing,
      and even a music player, all within a single page Backbone-driven app.
      Early on, the team decided to keep the site lightweight by using only
      Backbone.js and raw JavaScript. The result? Complete source code weighing
      in at a mere 350kb with feature-parity across the iPad, iPhone and web
      clients. The
      <a href="https://www.inkling.com/read/biology-neil-campbell-and-jane-reece-9th/chapter-1/overview-inquiring-about-life">free chapter</a>
      in every book makes it easy for anyone to try it out and take a look.
    </p>

    <div style="text-align: center;">
      <a href="http://inkling.com">
        <img width="550" height="361" data-original="docs/images/inkling.png" alt="Inkling" class="example_image" />
      </a>
    </div>

    <h2 id="examples-code-school">Code School</h2>

    <p>
      <a href="http://www.codeschool.com">Code School</a> courses teach people
      about various programming topics like <a href="http://coffeescript.org">CoffeeScript</a>, CSS, Ruby on Rails,
      and more. The new Code School course
      <a href="http://coffeescript.codeschool.com/levels/1/challenges/1">challenge page</a>
      is built from the ground up on Backbone.js, using
      everything it has to offer: the router, collections, models, and complex
      event handling. Before, the page was a mess of <a href="http://jquery.com/">jQuery</a> DOM manipulation
      and manual Ajax calls. Backbone.js helped introduce a new way to
      think about developing an organized front-end application in Javascript.
    </p>

    <div style="text-align: center;">
      <a href="http://www.codeschool.com">
        <img width="550" height="482" data-original="docs/images/code-school.png" alt="Code School" class="example_image" />
      </a>
    </div>

    <h2 id="examples-cloudapp">CloudApp</h2>

    <p>
      <a href="http://getcloudapp.com">CloudApp</a> is simple file and link
      sharing for the Mac. Backbone.js powers the web tools
      which consume the <a href="http://developer.getcloudapp.com">documented API</a>
      to manage Drops. Data is either pulled manually or pushed by
      <a href="http://pusher.com">Pusher</a> and fed to
      <a href="http://github.com/janl/mustache.js">Mustache</a> templates for
      rendering. Check out the <a href="http://cloudapp.github.com/engine">annotated source code</a>
      to see the magic.
    </p>

    <div style="text-align: center;">
      <a href="http://getcloudapp.com">
        <img width="550" height="426" data-original="docs/images/cloudapp.png" alt="CloudApp" class="example_image" />
      </a>
    </div>

    <h2 id="examples-seatgeek">SeatGeek</h2>

    <p>
      <a href="http://seatgeek.com">SeatGeek</a>'s stadium ticket maps were originally
      developed with <a href="http://prototypejs.org/">Prototype.js</a>. Moving to Backbone.js and <a href="http://jquery.com/">jQuery</a> helped organize
      a lot of the UI code, and the increased structure has made adding features
      a lot easier. SeatGeek is also in the process of building a mobile
      interface that will be Backbone.js from top to bottom.
    </p>

    <div style="text-align: center;">
      <a href="http://seatgeek.com">
        <img width="550" height="455" data-original="docs/images/seatgeek.png" alt="SeatGeek" class="example_image" />
      </a>
    </div>

    <h2 id="examples-easel">Easel</h2>

    <p>
      <a href="http://easel.io">Easel</a> is an in-browser, high fidelity web
      design tool that integrates with your design and development
      process. The Easel team uses CoffeeScript, Underscore.js and Backbone.js for
      their <a href="http://easel.io/demo">rich visual editor</a> as well as other
      management functions throughout the site. The structure of Backbone allowed
      the team to break the complex problem of building a visual editor into
      manageable components and still move quickly.
    </p>

    <div style="text-align: center;">
      <a href="http://easel.io">
        <img width="550" height="395" data-original="docs/images/easel.png" alt="Easel" class="example_image" />
      </a>
    </div>

    <h2 id="examples-prose">Prose</h2>

    <p>
      <a href="http://prose.io">Prose</a> is a content editor for GitHub,
      optimized for managing websites built with
      <a href="http://jekyllrb.com/">Jekyll</a> and Github Pages. Prose is
      itself implemented as a static Jekyll site, using Backbone.js to render
      the views and handle the routes, as well as
      <a href="http://github.com/michael/github">Github.js</a>, a small data
      abstraction layer for manipulating files directly on Github. Read more in the
      <a href="http://developmentseed.org/blog/2012/june/25/prose-a-content-editor-for-github/">official introduction post</a>,
      or <a href="https://github.com/prose/prose">take a look at the source code</a>.
    </p>

    <div style="text-align: center;">
      <a href="http://prose.io">
        <img width="550" height="447" data-original="docs/images/prose.png" alt="Prose" class="example_image" />
      </a>
    </div>


    <h2 id="examples-grove">Grove.io</h2>

    <p>
      <a href="http://grove.io">Grove.io</a> provides hosted IRC for teams.
      Backbone.js powers Grove's web client together with <a href="http://handlebarsjs.com/">Handlebars.js templating</a>.
      Updates to chat stream are pulled in realtime using long-polling.
    </p>

    <div style="text-align: center;">
      <a href="http://grove.io">
        <img width="550" height="415" data-original="docs/images/grove.png" alt="Grove.io" class="example_image" />
      </a>
    </div>

    <h2 id="examples-kanogames">KANO/GAMES</h2>

    <p>
      <a href="http://www.kanoapps.com/">KANO/APPS</a> used Backbone.js to create
      <a href="http://www.kanogames.com/">KANO/GAMES</a>, a social gaming website.
      KANO/GAMES relies on Backbone.js for almost every aspect of the site:
      for seamless page loading, to construct menus, game listings and game
      canvases, to build interactive HTML5 avatars, and for
      user and developer profiles, and live feeds.
    </p>

    <div style="text-align: center;">
      <a href="http://www.kanogames.com/">
        <img width="550" height="361" data-original="docs/images/kanogames.png" alt="KANO/GAMES" class="example_image" />
      </a>
    </div>

    <h2 id="examples-shortmail">Shortmail</h2>

    <p>
      <a href="http://410labs.com/">410 Labs</a> uses Backbone.js at
      <a href="http://shortmail.com/">Shortmail.com</a> to build a
      fast and responsive inbox, driven by the <a href="#Router">Router</a>.
      Backbone works with a <a href="http://rubyonrails.org/">Rails</a> backend to provide inbox rendering, archiving,
      replying, composing, and even a changes feed. Using Backbone's event-driven
      model and pushing the rendering and interaction logic to the front-end
      has not only simplified the view code, it has also drastically reduced the
      load on Shortmail's servers.
    </p>

    <div style="text-align: center;">
      <a href="http://shortmail.com">
        <img width="550" height="429" data-original="docs/images/shortmail.png" alt="Shortmail" class="example_image" />
      </a>
    </div>

    <h2 id="examples-scrollkit">scroll kit</h2>

    <p>
      <a href="http://scrollkit.com/">scroll kit</a> is a new kind of website
      builder that makes designing a web page feel more like drawing.
      The workspace is a single-page web application built with Rails and Backbone.js.
      In scroll kit, every DOM element is associated with a Backbone model, so that
      style changes that are made to an element automatically update the model
      and propagate the change across all its views.
      <a href="http://scrollkit.com/demo">Try it out</a>.
    </p>

    <div style="text-align: center;">
      <a href="http://scrollkit.com">
        <img width="550" height="453" data-original="docs/images/scrollkit.png" alt="scroll kit" class="example_image" />
      </a>
    </div>

    <h2 id="examples-battlefield">Battlefield Play4Free</h2>

    <p>
      <a href="http://battlefield.play4free.com/">Battlefield Play4Free</a> is
      the latest free-to-play first person shooter from the same team that
      created Battlefield Heroes. The in-game HTML5 front-end for makes heavy use of
      Backbone's views, models and collections to help keep the code modular
      and structured.
    </p>

    <div style="text-align: center;">
      <a href="http://battlefield.play4free.com/">
        <img width="550" height="435" data-original="docs/images/battlefield.png" alt="Battlefield Play4Free" class="example_image" />
      </a>
    </div>

    <h2 id="examples-salon">Salon.io</h2>

    <p>
      <a href="http://salon.io">Salon.io</a> provides a space where photographers,
      artists and designers freely arrange their visual art on virtual walls.
      <a href="http://salon.io">Salon.io</a> runs on <a href="http://rubyonrails.org/">Rails</a>, but does not use
      much of the traditional stack, as the entire frontend is designed as a
      single page web app, using Backbone.js, <a href="http://brunch.io/">Brunch</a> and
      <a href="http://coffeescript.org">CoffeeScript</a>.
    </p>

    <div style="text-align: center;">
      <a href="http://salon.io">
        <img width="550" height="483" data-original="docs/images/salon.png" alt="Salon.io" class="example_image" />
      </a>
    </div>

    <h2 id="examples-tilemill">TileMill</h2>

    <p>
      Our fellow
      <a href="http://www.newschallenge.org/">Knight Foundation News Challenge</a>
      winners, <a href="http://mapbox.com/">MapBox</a>, created an open-source
      map design studio with Backbone.js:
      <a href="http://mapbox.github.com/tilemill/">TileMill</a>.
      TileMill lets you manage map layers based on shapefiles and rasters, and
      edit their appearance directly in the browser with the
      <a href="https://github.com/mapbox/carto">Carto styling language</a>.
      Note that the gorgeous <a href="http://mapbox.com/">MapBox</a> homepage
      is also a Backbone.js app.
    </p>

    <div style="text-align: center;">
      <a href="http://mapbox.github.com/tilemill/">
        <img width="544" height="375" data-original="docs/images/tilemill.png" alt="TileMill" class="example_image" />
      </a>
    </div>

    <h2 id="examples-blossom">Blossom</h2>

    <p>
      <a href="http://blossom.io">Blossom</a> is a lightweight project management
      tool for lean teams. Backbone.js is heavily used in combination with
      <a href="http://coffeescript.org">CoffeeScript</a> to provide a smooth
      interaction experience. The app is packaged with <a href="http://brunch.io">Brunch</a>.
      The RESTful backend is built with <a href="http://flask.pocoo.org/">Flask</a> on Google App Engine.
    </p>

    <div style="text-align: center;">
      <a href="http://blossom.io">
        <img width="550" height="367" data-original="docs/images/blossom.png" alt="Blossom" class="example_image" />
      </a>
    </div>

    <h2 id="examples-decide">Decide</h2>

    <p>
      <a href="http://decide.com">Decide.com</a> helps people decide when to buy
      consumer electronics. It relies heavily on Backbone.js to render and
      update its Search Results Page. An "infinite scroll" feature takes
      advantage of a SearchResults model containing a collection of
      Product models to fetch more results and render them on the fly
      with <a href="http://mustache.github.com">Mustache</a>. A SearchController keeps everything in sync and
      maintains page state in the URL. Backbone also powers the user
      accounts and settings management.
    </p>

    <div style="text-align: center;">
      <a href="http://decide.com">
        <img width="550" height="449" data-original="docs/images/decide.png" alt="Decide" class="example_image" />
      </a>
    </div>

    <h2 id="examples-trello">Trello</h2>

    <p>
      <a href="http://trello.com">Trello</a> is a collaboration tool that
      organizes your projects into boards. A Trello board holds many lists of
      cards, which can contain checklists, files and conversations, and may be
      voted on and organized with labels. Updates on the board happen in
      real time. The site was built ground up using Backbone.js for all the
      models, views, and routes.
    </p>

    <div style="text-align: center;">
      <a href="http://trello.com">
        <img width="550" height="416" data-original="docs/images/trello.png" alt="Trello" class="example_image" />
      </a>
    </div>

    <h2 id="examples-ducksboard">Ducksboard</h2>

    <p>
    <a href="http://ducksboard.com/">Ducksboard</a> is an online dashboard
      for your SaaS and business metrics, built with
      <a href="http://twistedmatrix.com/">Twisted</a> and
      <a href="http://www.djangoproject.com/">Django</a> and using WebSockets.
      It can fetch data from popular providers or accept input through
      a simple API.
      Backbone is used throughout Ducksboard's interface, every widget,
      dashboard and SaaS account is a Backbone model with several views
      (data display, configuration view). A
      <a href="https://public.ducksboard.com/BFVzKVPeOoWRsL0VZ8MZ/">live demo</a>
      is available.
    </p>

    <div style="text-align: center;">
      <a href="http://ducksboard.com/">
        <img width="550" height="322" data-original="docs/images/ducksboard.png" alt="Ducksboard" class="example_image" />
      </a>
    </div>

    <h2 id="examples-quietwrite">QuietWrite</h2>

    <p>
      <a href="http://www.twitter.com/jamesjyu">James Yu</a> used Backbone.js to
      create <a href="http://www.quietwrite.com/">QuietWrite</a>, an app
      that gives writers a clean and quiet interface to concentrate on the text itself.
      The editor relies on Backbone to persist document data to the server. He
      followed up with a Backbone.js + <a href="http://rubyonrails.org/">Rails</a> tutorial that describes how to implement
      <a href="http://www.jamesyu.org/2011/01/27/cloudedit-a-backbone-js-tutorial-by-example/">CloudEdit, a simple document editing app</a>.
    </p>

    <div style="text-align: center;">
      <a href="http://www.quietwrite.com/">
        <img width="550" height="381" data-original="docs/images/quietwrite.png" alt="QuietWrite" class="example_image" />
      </a>
    </div>

    <h2 id="examples-tzigla">Tzigla</h2>

    <p>
      <a href="http://twitter.com/evilchelu">Cristi Balan</a> and
      <a href="http://dira.ro">Irina Dumitrascu</a> created
      <a href="http://tzigla.com">Tzigla</a>, a collaborative drawing
      application where artists make tiles that connect to each other to
      create <a href="http://tzigla.com/boards/1">surreal drawings</a>.
      Backbone models help organize the code, routers provide
      <a href="http://tzigla.com/boards/1#!/tiles/2-2">bookmarkable deep links</a>,
      and the views are rendered with
      <a href="https://github.com/creationix/haml-js">haml.js</a> and
      <a href="http://zeptojs.com/">Zepto</a>.
      Tzigla is written in Ruby (<a href="http://rubyonrails.org/">Rails</a>) on the backend, and
      <a href="http://coffeescript.org">CoffeeScript</a> on the frontend, with
      <a href="http://documentcloud.github.com/jammit/">Jammit</a>
      prepackaging the static assets.
    </p>

    <div style="text-align: center;">
      <a href="http://www.tzigla.com/">
        <img width="550" height="376" data-original="docs/images/tzigla.png" alt="Tzigla" class="example_image" />
      </a>
    </div>

    <h2 id="faq">F.A.Q.</h2>

    <p id="FAQ-events">
      <b class="header">Catalog of Events</b>
      <br />
      Here's a list of all of the built-in events that Backbone.js can fire.
      You're also free to trigger your own events on Models and Views as you
      see fit.
    </p>

    <ul class="small">
      <li><b>"add"</b> (model, collection, options) &mdash; when a model is added to a collection. </li>
      <li><b>"remove"</b> (model, collection, options) &mdash; when a model is removed from a collection. </li>
      <li><b>"reset"</b> (collection, options) &mdash; when the collection's entire contents have been replaced. </li>
      <li><b>"change"</b> (model, options) &mdash; when a model's attributes have changed. </li>
      <li><b>"change:[attribute]"</b> (model, value, options) &mdash; when a specific attribute has been updated. </li>
      <li><b>"destroy"</b> (model, collection, options) &mdash; when a model is <a href="#Model-destroy">destroyed</a>. </li>
      <li><b>"sync"</b> (model, resp, options) &mdash; triggers whenever a model has been successfully synced to the server. </li>
      <li><b>"error"</b> (model, collection) &mdash; when a model's validation fails, or a <a href="#Model-save">save</a> call fails on the server. </li>
      <li><b>"route:[name]"</b> (router) &mdash; when one of a router's routes has matched. </li>
      <li><b>"all"</b> &mdash; this special event fires for <i>any</i> triggered event, passing the event name as the first argument. </li>
    </ul>

    <p id="FAQ-tim-toady">
      <b class="header">There's More Than One Way To Do It</b>
      <br />
      It's common for folks just getting started to treat the examples listed
      on this page as some sort of gospel truth. In fact, Backbone.js is intended
      to be fairly agnostic about many common patterns in client-side code.
      For example...
    </p>

    <p>
      <b>References between Models and Views</b> can be handled several ways.
      Some people like to have direct pointers, where views correspond 1:1 with
      models (<tt>model.view</tt> and <tt>view.model</tt>). Others prefer to have intermediate
      "controller" objects that orchestrate the creation and organization of
      views into a hierarchy. Others still prefer the evented approach, and always
      fire events instead of calling methods directly. All of these styles work well.
    </p>

    <p>
      <b>Batch operations</b> on Models are common, but often best handled differently
      depending on your server-side setup. Some folks don't mind making individual
      Ajax requests. Others create explicit resources for RESTful batch operations:
      <tt>/notes/batch/destroy?ids=1,2,3,4</tt>. Others tunnel REST over JSON, with the
      creation of "changeset" requests:
    </p>

<pre>
  {
    "create":  [array of models to create]
    "update":  [array of models to update]
    "destroy": [array of model ids to destroy]
  }
</pre>

    <p>
      <b>Feel free to define your own events.</b> <a href="#Events">Backbone.Events</a>
      is designed so that you can mix it in to any JavaScript object or prototype.
      Since you can use any string as an event, it's often handy to bind
      and trigger your own custom events: <tt>model.on("selected:true")</tt> or
      <tt>model.on("editing")</tt>
    </p>

    <p>
      <b>Render the UI</b> as you see fit. Backbone is agnostic as to whether you
      use <a href="http://underscorejs.org/#template">Underscore templates</a>,
      <a href="https://github.com/janl/mustache.js">Mustache.js</a>, direct DOM
      manipulation, server-side rendered snippets of HTML, or
      <a href="http://jqueryui.com/">jQuery UI</a> in your <tt>render</tt> function.
      Sometimes you'll create a view for each model ... sometimes you'll have a
      view that renders thousands of models at once, in a tight loop. Both can be
      appropriate in the same app, depending on the quantity of data involved,
      and the complexity of the UI.
    </p>

    <p id="FAQ-nested">
      <b class="header">Nested Models &amp; Collections</b>
      <br />
      It's common to nest collections inside of models with Backbone. For example,
      consider a <tt>Mailbox</tt> model that contains many <tt>Message</tt> models.
      One nice pattern for handling this is have a <tt>this.messages</tt> collection
      for each mailbox, enabling the lazy-loading of messages, when the mailbox
      is first opened ... perhaps with <tt>MessageList</tt> views listening for
      <tt>"add"</tt> and <tt>"remove"</tt> events.
    </p>

<pre>
var Mailbox = Backbone.Model.extend({

  initialize: function() {
    this.messages = new Messages;
    this.messages.url = '/mailbox/' + this.id + '/messages';
    this.messages.on("reset", this.updateCounts);
  },

  ...

});

var Inbox = new Mailbox;

// And then, when the Inbox is opened:

Inbox.messages.fetch();
</pre>

    <p>
      If you're looking for something more opinionated, there are a number of
      Backbone plugins that add sophisticated associations among models,
      <a href="https://github.com/documentcloud/backbone/wiki/Extensions%2C-Plugins%2C-Resources">available on the wiki</a>.
    </p>

    <p>
      Backbone doesn't include direct support for nested models and collections
      or "has many" associations because there are a number
      of good patterns for modeling structured data on the client side, and
      <i>Backbone should provide the foundation for implementing any of them.</i>
      You may want to&hellip;
    </p>

    <ul>
      <li>
        Mirror an SQL database's structure, or the structure of a NoSQL database.
      </li>
      <li>
        Use models with arrays of "foreign key" ids, and join to top level
        collections (a-la tables).
      </li>
      <li>
        For associations that are numerous, use a range of ids instead of an
        explicit list.
      </li>
      <li>
        Avoid ids, and use direct references, creating a partial object graph
        representing your data set.
      </li>
      <li>
        Lazily load joined models from the server, or lazily deserialize nested
        models from JSON documents.
      </li>
    </ul>

    <p id="FAQ-bootstrap">
      <b class="header">Loading Bootstrapped Models</b>
      <br />
      When your app first loads, it's common to have a set of initial models that
      you know you're going to need, in order to render the page. Instead of
      firing an extra AJAX request to <a href="#Collection-fetch">fetch</a> them,
      a nicer pattern is to have their data already bootstrapped into the page.
      You can then use <a href="#Collection-reset">reset</a> to populate your
      collections with the initial data. At DocumentCloud, in the
      <a href="http://en.wikipedia.org/wiki/ERuby">ERB</a> template for the
      workspace, we do something along these lines:
    </p>

<pre>
&lt;script&gt;
  var Accounts = new Backbone.Collection;
  Accounts.reset(&lt;%= @accounts.to_json %&gt;);
  var Projects = new Backbone.Collection;
  Projects.reset(&lt;%= @projects.to_json(:collaborators => true) %&gt;);
&lt;/script&gt;
</pre>

    <p>You have to <a href="http://mathiasbynens.be/notes/etago">escape</a>
    <tt>&lt;/</tt> within the JSON string, to prevent javascript injection
    attacks.

    <p id="FAQ-extending">
      <b class="header">Extending Backbone</b>
      <br />
      Many JavaScript libraries are meant to be insular and self-enclosed,
      where you interact with them by calling their public API, but never peek
      inside at the guts. Backbone.js is <i>not</i> that kind of library.
    </p>

    <p>
      Because it serves as a foundation for your application, you're meant to
      extend and enhance it in the ways you see fit &mdash; the entire source
      code is <a href="docs/backbone.html">annotated</a> to make this easier
      for you. You'll find that there's very little there apart from core
      functions, and most of those can be overriden or augmented should you find
      the need. If you catch yourself adding methods to <tt>Backbone.Model.prototype</tt>,
      or creating your own base subclass, don't worry &mdash; that's how things are
      supposed to work.
    </p>

    <p id="FAQ-mvc">
      <b class="header">How does Backbone relate to "traditional" MVC?</b>
      <br />
      Different implementations of the
      <a href="http://en.wikipedia.org/wiki/Model–View–Controller">Model-View-Controller</a>
      pattern tend to disagree about the definition of a controller. If it helps any, in
      Backbone, the <a href="#View">View</a> class can also be thought of as a
      kind of controller, dispatching events that originate from the UI, with
      the HTML template serving as the true view. We call it a View because it
      represents a logical chunk of UI, responsible for the contents of a single
      DOM element.
    </p>

    <p>
      Comparing the overall structure of Backbone to a server-side MVC framework
      like <b>Rails</b>, the pieces line up like so:
    </p>

    <ul>
      <li>
        <b>Backbone.Model</b> &ndash; Like a Rails model minus the class
        methods. Wraps a row of data in business logic.
      </li>
      <li>
        <b>Backbone.Collection</b> &ndash; A group of models on the client-side,
        with sorting/filtering/aggregation logic.
      </li>
      <li>
        <b>Backbone.Router</b> &ndash; Rails <tt>routes.rb</tt> + Rails controller
        actions. Maps URLs to functions.
      </li>
      <li>
        <b>Backbone.View</b> &ndash; A logical, re-usable piece of UI. Often,
        but not always, associated with a model.
      </li>
      <li>
        <b>Client-side Templates</b> &ndash; Rails <tt>.html.erb</tt> views,
        rendering a chunk of HTML.
      </li>
    </ul>

    <p id="FAQ-this">
      <b class="header">Binding "this"</b>
      <br />
      Perhaps the single most common JavaScript "gotcha" is the fact that when
      you pass a function as a callback, its value for <tt>this</tt> is lost. With
      Backbone, when dealing with <a href="#Events">events</a> and callbacks,
      you'll often find it useful to rely on
      <a href="http://underscorejs.org/#bind">_.bind</a> and
      <a href="http://underscorejs.org/#bindAll">_.bindAll</a>
      from Underscore.js.
    </p>

    <p>
      When binding callbacks to Backbone events, you can choose to pass an optional
      third argument to specify the <tt>this</tt> that will be used when the
      callback is later invoked:
    </p>

<pre>
var MessageList = Backbone.View.extend({

  initialize: function() {
    var messages = this.collection;
    messages.on("reset", this.render, this);
    messages.on("add", this.addMessage, this);
    messages.on("remove", this.removeMessage, this);
  }

});

// Later, in the app...

Inbox.messages.add(newMessage);
</pre>

    <p id="FAQ-rails">
      <b class="header">Working with Rails</b>
      <br />
      Backbone.js was originally extracted from
      <a href="http://www.documentcloud.org">a Rails application</a>; getting
      your client-side (Backbone) Models to sync correctly with your server-side
      (Rails) Models is painless, but there are still a few things to be aware of.
    </p>

    <p>
      By default, Rails versions prior to 3.1 add an extra layer of wrapping
      around the JSON representation of models. You can disable this wrapping
      by setting:
    </p>

<pre>
ActiveRecord::Base.include_root_in_json = false
</pre>

    <p>
      ... in your configuration. Otherwise, override
      <a href="#Model-parse">parse</a> to pull model attributes out of the
      wrapper. Similarly, Backbone PUTs and POSTs direct JSON representations
      of models, where by default Rails expects namespaced attributes. You can
      have your controllers filter attributes directly from <tt>params</tt>, or
      you can override <a href="#Model-toJSON">toJSON</a> in Backbone to add
      the extra wrapping Rails expects.
    </p>

    <h2 id="changelog">Change Log</h2>

    <b class="header">0.9.2</b> &mdash; <small><i>March 21, 2012</i></small> &mdash; <a href="https://github.com/documentcloud/backbone/compare/0.9.1...0.9.2">Diff</a><br />
    <ul style="margin-top: 5px;">
      <li>
        Instead of throwing an error when adding duplicate models to a collection,
        Backbone will now silently skip them instead.
      </li>
      <li>
        Added <a href="#Collection-push">push</a>,
        <a href="#Collection-pop">pop</a>,
        <a href="#Collection-unshift">unshift</a>, and
        <a href="#Collection-shift">shift</a> to collections.
      </li>
      <li>
        A model's <a href="#Model-changed">changed</a> hash is now exposed for
        easy reading of the changed attribute delta, since the model's last
        <tt>"change"</tt> event.
      </li>
      <li>
        Added <a href="#Collection-where">where</a> to collections for simple
        filtering.
      </li>
      <li>
        You can now use a single <a href="#Events-off">off</a> call
        to remove all callbacks bound to a specific object.
      </li>
      <li>
        Bug fixes for nested individual change events, some of which may be
        "silent".
      </li>
      <li>
        Bug fixes for URL encoding in <tt>location.hash</tt> fragments.
      </li>
      <li>
        Bug fix for client-side validation in advance of a <tt>save</tt> call
        with <tt>{wait: true}</tt>.
      </li>
      <li>
        Updated / refreshed the example
        <a href="examples/todos/index.html">Todo List</a> app.
      </li>
    </ul>

    <b class="header">0.9.1</b> &mdash; <small><i>Feb. 2, 2012</i></small> &mdash; <a href="https://github.com/documentcloud/backbone/compare/0.9.0...0.9.1">Diff</a><br />
    <ul style="margin-top: 5px;">
      <li>
        Reverted to 0.5.3-esque behavior for validating models. Silent changes
        no longer trigger validation (making it easier to work with forms).
        Added an <tt>isValid</tt> function that you can use to check if a model
        is currently in a valid state.
      </li>
      <li>
        If you have multiple versions of jQuery on the page, you can now tell
        Backbone which one to use with <tt>Backbone.setDomLibrary</tt>.
      </li>
      <li>
        Fixes regressions in <b>0.9.0</b> for routing with "root", saving with
        both "wait" and "validate", and the order of nested "change" events.
      </li>
    </ul>

    <b class="header">0.9.0</b> &mdash; <small><i>Jan. 30, 2012</i></small> &mdash; <a href="https://github.com/documentcloud/backbone/compare/0.5.3...0.9.0">Diff</a><br />
    <ul style="margin-top: 5px;">
      <li>
        Creating and destroying models with <tt>create</tt> and <tt>destroy</tt>
        are now optimistic by default. Pass <tt>{wait: true}</tt> as an option
        if you'd like them to wait for a successful server response to proceed.
      </li>
      <li>
        Two new properties on views: <tt>$el</tt> &mdash; a cached jQuery (or Zepto)
        reference to the view's element, and <tt>setElement</tt>, which should
        be used instead of manually setting a view's <tt>el</tt>. It will
        both set <tt>view.el</tt> and <tt>view.$el</tt> correctly, as well as
        re-delegating events on the new DOM element.
      </li>
      <li>
        You can now bind and trigger multiple spaced-delimited events at once.
        For example: <tt>model.on("change:name change:age", ...)</tt>
      </li>
      <li>
        When you don't know the key in advance, you may now call
        <tt>model.set(key, value)</tt> as well as <tt>save</tt>.
      </li>
      <li>
        Multiple models with the same <tt>id</tt> are no longer allowed in a
        single collection.
      </li>
      <li>
        Added a <tt>"sync"</tt> event, which triggers whenever a model's state
        has been successfully synced with the server (create, save, destroy).
      </li>
      <li>
        <tt>bind</tt> and <tt>unbind</tt> have been renamed to <tt>on</tt>
        and <tt>off</tt> for clarity, following jQuery's lead.
        The old names are also still supported.
      </li>
      <li>
        A Backbone collection's <tt>comparator</tt> function may now behave
        either like a <a href="http://underscorejs.org/#sortBy">sortBy</a>
        (pass a function that takes a single argument),
        or like a <a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/sort">sort</a>
        (pass a comparator function that expects two arguments). The comparator
        function is also now bound by default to the collection &mdash; so you
        can refer to <tt>this</tt> within it.
      </li>
      <li>
        A view's <tt>events</tt> hash may now also contain direct function
        values as well as the string names of existing view methods.
      </li>
      <li>
        Validation has gotten an overhaul &mdash; a model's <tt>validate</tt> function
        will now be run even for silent changes, and you can no longer create
        a model in an initially invalid state.
      </li>
      <li>
        Added <tt>shuffle</tt> and <tt>initial</tt> to collections, proxied
        from Underscore.
      </li>
      <li>
        <tt>Model#urlRoot</tt> may now be defined as a function as well as a
        value.
      </li>
      <li>
        <tt>View#attributes</tt> may now be defined as a function as well as a
        value.
      </li>
      <li>
        Calling <tt>fetch</tt> on a collection will now cause all fetched JSON
        to be run through the collection's model's <tt>parse</tt> function, if
        one is defined.
      </li>
      <li>
        You may now tell a router to <tt>navigate(fragment, {replace: true})</tt>,
        which will either use <tt>history.replaceState</tt> or
        <tt>location.hash.replace</tt>, in order to change the URL without adding
        a history entry.
      </li>
      <li>
        Within a collection's <tt>add</tt> and <tt>remove</tt> events, the index
        of the model being added or removed is now available as <tt>options.index</tt>.
      </li>
      <li>
        Added an <tt>undelegateEvents</tt> to views, allowing you to manually
        remove all configured event delegations.
      </li>
      <li>
        Although you shouldn't be writing your routes with them in any case &mdash;
        leading slashes (<tt>/</tt>) are now stripped from routes.
      </li>
      <li>
        Calling <tt>clone</tt> on a model now only passes the attributes
        for duplication, not a reference to the model itself.
      </li>
      <li>
        Calling <tt>clear</tt> on a model now removes the <tt>id</tt> attribute.
      </li>
    </ul>

    <p>
      <b class="header">0.5.3</b> &mdash; <small><i>August 9, 2011</i></small><br />
      A View's <tt>events</tt> property may now be defined as a function, as well
      as an object literal, making it easier to programmatically define and inherit
      events. <tt>groupBy</tt> is now proxied from Underscore as a method on Collections.
      If the server has already rendered everything on page load, pass
      <tt>Backbone.history.start({silent: true})</tt> to prevent the initial route
      from triggering. Bugfix for pushState with encoded URLs.
    </p>

    <p>
      <b class="header">0.5.2</b> &mdash; <small><i>July 26, 2011</i></small><br />
      The <tt>bind</tt> function, can now take an optional third argument, to specify
      the <tt>this</tt> of the callback function.
      Multiple models with the same <tt>id</tt> are now allowed in a collection.
      Fixed a bug where calling <tt>.fetch(jQueryOptions)</tt> could cause an
      incorrect URL to be serialized.
      Fixed a brief extra route fire before redirect, when degrading from
      <tt>pushState</tt>.
    </p>

    <p>
      <b class="header">0.5.1</b> &mdash; <small><i>July 5, 2011</i></small><br />
      Cleanups from the 0.5.0 release, to wit: improved transparent upgrades from
      hash-based URLs to pushState, and vice-versa. Fixed inconsistency with
      non-modified attributes being passed to <tt>Model#initialize</tt>. Reverted
      a <b>0.5.0</b> change that would strip leading hashbangs from routes.
      Added <tt>contains</tt> as an alias for <tt>includes</tt>.
    </p>

    <p>
      <b class="header">0.5.0</b> &mdash; <small><i>July 1, 2011</i></small><br />
      A large number of tiny tweaks and micro bugfixes, best viewed by looking
      at <a href="https://github.com/documentcloud/backbone/compare/0.3.3...0.5.0">the commit diff</a>.
      HTML5 <tt>pushState</tt> support, enabled by opting-in with:
      <tt>Backbone.history.start({pushState: true})</tt>.
      <tt>Controller</tt> was renamed to <tt>Router</tt>, for clarity.
      <tt>Collection#refresh</tt> was renamed to <tt>Collection#reset</tt> to emphasize
      its ability to both reset the collection with new models, as well as empty
      out the collection when used with no parameters.
      <tt>saveLocation</tt> was replaced with <tt>navigate</tt>.
      RESTful persistence methods (save, fetch, etc.) now return the jQuery deferred
      object for further success/error chaining and general convenience.
      Improved XSS escaping for <tt>Model#escape</tt>.
      Added a <tt>urlRoot</tt> option to allow specifying RESTful urls without
      the use of a collection.
      An error is thrown if <tt>Backbone.history.start</tt> is called multiple times.
      <tt>Collection#create</tt> now validates before initializing the new model.
      <tt>view.el</tt> can now be a jQuery string lookup.
      Backbone Views can now also take an <tt>attributes</tt> parameter.
      <tt>Model#defaults</tt> can now be a function as well as a literal attributes
      object.
    </p>

    <p>
      <b class="header">0.3.3</b> &mdash; <small><i>Dec 1, 2010</i></small><br />
      Backbone.js now supports <a href="http://zeptojs.com">Zepto</a>, alongside
      jQuery, as a framework for DOM manipulation and Ajax support.
      Implemented <a href="#Model-escape">Model#escape</a>, to efficiently handle
      attributes intended for HTML interpolation. When trying to persist a model,
      failed requests will now trigger an <tt>"error"</tt> event. The
      ubiquitous <tt>options</tt> argument is now passed as the final argument
      to all <tt>"change"</tt> events.
    </p>

    <p>
      <b class="header">0.3.2</b> &mdash; <small><i>Nov 23, 2010</i></small><br />
      Bugfix for IE7 + iframe-based "hashchange" events. <tt>sync</tt> may now be
      overridden on a per-model, or per-collection basis. Fixed recursion error
      when calling <tt>save</tt> with no changed attributes, within a
      <tt>"change"</tt> event.
    </p>

    <p>
      <b class="header">0.3.1</b> &mdash; <small><i>Nov 15, 2010</i></small><br />
      All <tt>"add"</tt> and <tt>"remove"</tt> events are now sent through the
      model, so that views can listen for them without having to know about the
      collection. Added a <tt>remove</tt> method to <a href="#View">Backbone.View</a>.
      <tt>toJSON</tt> is no longer called at all for <tt>'read'</tt> and <tt>'delete'</tt> requests.
      Backbone routes are now able to load empty URL fragments.
    </p>

    <p>
      <b class="header">0.3.0</b> &mdash; <small><i>Nov 9, 2010</i></small><br />
      Backbone now has <a href="#Controller">Controllers</a> and
      <a href="#History">History</a>, for doing client-side routing based on
      URL fragments.
      Added <tt>emulateHTTP</tt> to provide support for legacy servers that don't
      do <tt>PUT</tt> and <tt>DELETE</tt>.
      Added <tt>emulateJSON</tt> for servers that can't accept <tt>application/json</tt>
      encoded requests.
      Added <a href="#Model-clear">Model#clear</a>, which removes all attributes
      from a model.
      All Backbone classes may now be seamlessly inherited by CoffeeScript classes.
    </p>

    <p>
      <b class="header">0.2.0</b> &mdash; <small><i>Oct 25, 2010</i></small><br />
      Instead of requiring server responses to be namespaced under a <tt>model</tt>
      key, now you can define your own <a href="#Model-parse">parse</a> method
      to convert responses into attributes for Models and Collections.
      The old <tt>handleEvents</tt> function is now named
      <a href="#View-delegateEvents">delegateEvents</a>, and is automatically
      called as part of the View's constructor.
      Added a <a href="#Collection-toJSON">toJSON</a> function to Collections.
      Added <a href="#Collection-chain">Underscore's chain</a> to Collections.
    </p>

    <p>
      <b class="header">0.1.2</b> &mdash; <small><i>Oct 19, 2010</i></small><br />
      Added a <a href="#Model-fetch">Model#fetch</a> method for refreshing the
      attributes of single model from the server.
      An <tt>error</tt> callback may now be passed to <tt>set</tt> and <tt>save</tt>
      as an option, which will be invoked if validation fails, overriding the
      <tt>"error"</tt> event.
      You can now tell backbone to use the <tt>_method</tt> hack instead of HTTP
      methods by setting <tt>Backbone.emulateHTTP = true</tt>.
      Existing Model and Collection data is no longer sent up unnecessarily with
      <tt>GET</tt> and <tt>DELETE</tt> requests. Added a <tt>rake lint</tt> task.
      Backbone is now published as an <a href="http://npmjs.org">NPM</a> module.
    </p>

    <p>
      <b class="header">0.1.1</b> &mdash; <small><i>Oct 14, 2010</i></small><br />
      Added a convention for <tt>initialize</tt> functions to be called
      upon instance construction, if defined. Documentation tweaks.
    </p>

    <p>
      <b class="header">0.1.0</b> &mdash; <small><i>Oct 13, 2010</i></small><br />
      Initial Backbone release.
    </p>

    <p>
      <br />
      <a href="http://documentcloud.org/" title="A DocumentCloud Project" style="background:none;">
        <img src="http://jashkenas.s3.amazonaws.com/images/a_documentcloud_project.png" alt="A DocumentCloud Project" style="position:relative;left:-10px;" />
      </a>
    </p>

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