Backbone.js (1.4.1)

-   » GitHub Repository
-   » Annotated Source

Getting Started

-   - Introduction
-   – Models and Views
-   – Collections
-   – API Integration
-   – Rendering
-   – Routing

Events

-   – on
-   – off
-   – trigger
-   – once
-   – listenTo
-   – stopListening
-   – listenToOnce
-   - Catalog of Built-in Events

Model

-   – extend
-   – preinitialize
-   – constructor / initialize
-   – get
-   – set
-   – escape
-   – has
-   – unset
-   – clear
-   – id
-   – idAttribute
-   – cid
-   – attributes
-   – changed
-   – defaults
-   – toJSON
-   – sync
-   – fetch
-   – save
-   – destroy
-   – Underscore Methods (9)
-   – validate
-   – validationError
-   – isValid
-   – url
-   – urlRoot
-   – parse
-   – clone
-   – isNew
-   – hasChanged
-   – changedAttributes
-   – previous
-   – previousAttributes

Collection

-   – extend
-   – model
-   – modelId
-   – preinitialize
-   – constructor / initialize
-   – models
-   – toJSON
-   – sync
-   – Underscore Methods (46)
-   – add
-   – remove
-   – reset
-   – set
-   – get
-   – at
-   – push
-   – pop
-   – unshift
-   – shift
-   – slice
-   – length
-   – comparator
-   – sort
-   – pluck
-   – where
-   – findWhere
-   – url
-   – parse
-   – clone
-   – fetch
-   – create
-   – mixin

Router

-   – extend
-   – routes
-   – preinitialize
-   – constructor / initialize
-   – route
-   – navigate
-   – execute

History

-   – start

Sync

-   – Backbone.sync
-   – Backbone.ajax
-   – Backbone.emulateHTTP
-   – Backbone.emulateJSON

View

-   – extend
-   – preinitialize
-   – constructor / initialize
-   – el
-   – $el
-   – setElement
-   – attributes
-   – $ (jQuery)
-   – template
-   – render
-   – remove
-   – events
-   – delegateEvents
-   – undelegateEvents

Utility

-   – Backbone.noConflict
-   – Backbone.$

F.A.Q.

-   – Why Backbone?
-   – More Than One Way To Do It
-   – Nested Models & Collections
-   – Loading Bootstrapped Models
-   – Extending Backbone
-   – Traditional MVC
-   – Binding "this"
-   – Working with Rails

Examples

-   – Todos
-   – DocumentCloud
-   – USA Today
-   – Rdio
-   – Hulu
-   – Quartz
-   – Earth
-   – Vox
-   – Gawker Media
-   – Flow
-   – Gilt Groupe
-   – Enigma
-   – NewsBlur
-   – WordPress.com
-   – Foursquare
-   – Bitbucket
-   – Disqus
-   – Delicious
-   – Khan Academy
-   – IRCCloud
-   – Pitchfork
-   – Spin
-   – ZocDoc
-   – Walmart Mobile
-   – Groupon Now!
-   – Basecamp
-   – Slavery Footprint
-   – Stripe
-   – Airbnb
-   – SoundCloud Mobile
-   - Art.sy
-   – Pandora
-   – Inkling
-   – Code School
-   – CloudApp
-   – SeatGeek
-   – Easel
-   - Jolicloud
-   – Salon.io
-   – TileMill
-   – Blossom
-   – Trello
-   – Tzigla

Change Log

[Backbone.js]

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

The project is hosted on GitHub, and the annotated source code is
available, as well as an online test suite, an example application, a
list of tutorials and a long list of real-world projects that use
Backbone. Backbone is available for use under the MIT software license.

You can report bugs and discuss features on the GitHub issues page, or
add pages to the wiki.

Backbone is an open-source component of DocumentCloud.

Downloads & Dependencies (Right-click, and use "Save As")

  ----------------------------------- -----------------------------------
  Development Version (1.4.1)         72kb, Full source, tons of comments

  Production Version (1.4.1)          7.9kb, Packed and gzipped
                                      (Source Map)

  Edge Version (master)               Unreleased, use at your own risk
  ----------------------------------- -----------------------------------

Backbone's only hard dependency is Underscore.js ( >= 1.8.3). For
RESTful persistence and DOM manipulation with Backbone.View, include
jQuery ( >= 1.11.0). (Mimics of the Underscore and jQuery APIs, such as
Lodash and Zepto, will also tend to work, with varying degrees of
compatibility.)

Getting Started

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.

With Backbone, you represent your data as Models, 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 "change"
event; all the Views 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 id, and update the HTML manually — when the
model changes, the views simply update themselves.

Philosophically, Backbone is an attempt to discover the minimal set of
data-structuring (models and collections) and user interface (views and
URLs) primitives that are generally useful when building web
applications with JavaScript. In an ecosystem where overarching,
decides-everything-for-you frameworks are commonplace, and many
libraries require your site to be reorganized to suit their look, feel,
and default behavior — Backbone should continue to be a tool that gives
you the freedom to design the full experience of your web application.

If you're new here, and aren't yet quite sure what Backbone is for,
start by browsing the list of Backbone-based projects.

Many of the code examples in this documentation are runnable, because
Backbone is included on this page. Click the play button to execute
them.

Models and Views

[Model-View Separation.]

The single most important thing that Backbone can help you with is
keeping your business logic separate from your user interface. When the
two are entangled, change is hard; when logic doesn't depend on UI, your
interface becomes easier to work with.

Model

-   Orchestrates data and business logic.
-   Loads and saves data from the server.
-   Emits events when data changes.

View

-   Listens for changes and renders UI.
-   Handles user input and interactivity.
-   Sends captured input to the model.

A Model manages an internal table of data attributes, and triggers
"change" events when any of its data is modified. Models handle syncing
data with a persistence layer — usually a REST API with a backing
database. Design your models as the atomic reusable objects containing
all of the helpful functions for manipulating their particular bit of
data. Models should be able to be passed around throughout your app, and
used anywhere that bit of data is needed.

A View is an atomic chunk of user interface. It often renders the data
from a specific model, or number of models — but views can also be
data-less chunks of UI that stand alone. Models should be generally
unaware of views. Instead, views listen to the model "change" events,
and react or re-render themselves appropriately.

Collections

[Model Collections.]

A Collection helps you deal with a group of related models, handling the
loading and saving of new models to the server and providing helper
functions for performing aggregations or computations against a list of
models. Aside from their own events, collections also proxy through all
of the events that occur to models within them, allowing you to listen
in one place for any change that might happen to any model in the
collection.

API Integration

Backbone is pre-configured to sync with a RESTful API. Simply create a
new Collection with the url of your resource endpoint:

    var Books = Backbone.Collection.extend({
      url: '/books'
    });

The Collection and Model components together form a direct mapping of
REST resources using the following methods:

    GET  /books/ .... collection.fetch();
    POST /books/ .... collection.create();
    GET  /books/1 ... model.fetch();
    PUT  /books/1 ... model.save();
    DEL  /books/1 ... model.destroy();

When fetching raw JSON data from an API, a Collection will automatically
populate itself with data formatted as an array, while a Model will
automatically populate itself with data formatted as an object:

    [{"id": 1}] ..... populates a Collection with one model.
    {"id": 1} ....... populates a Model with one attribute.

However, it's fairly common to encounter APIs that return data in a
different format than what Backbone expects. For example, consider
fetching a Collection from an API that returns the real data array
wrapped in metadata:

    {
      "page": 1,
      "limit": 10,
      "total": 2,
      "books": [
        {"id": 1, "title": "Pride and Prejudice"},
        {"id": 4, "title": "The Great Gatsby"}
      ]
    }

In the above example data, a Collection should populate using the
"books" array rather than the root object structure. This difference is
easily reconciled using a parse method that returns (or transforms) the
desired portion of API data:

    var Books = Backbone.Collection.extend({
      url: '/books',
      parse: function(data) {
        return data.books;
      }
    });

View Rendering

[View rendering.]

Each View manages the rendering and user interaction within its own DOM
element. If you're strict about not allowing views to reach outside of
themselves, it helps keep your interface flexible — allowing views to be
rendered in isolation in any place where they might be needed.

Backbone remains unopinionated about the process used to render View
objects and their subviews into UI: you define how your models get
translated into HTML (or SVG, or Canvas, or something even more exotic).
It could be as prosaic as a simple Underscore template, or as fancy as
the React virtual DOM. Some basic approaches to rendering views can be
found in the Backbone primer.

Routing with URLs

[Routing]

In rich web applications, we still want to provide linkable,
bookmarkable, and shareable URLs to meaningful locations within an app.
Use the Router to update the browser URL whenever the user reaches a new
"place" in your app that they might want to bookmark or share.
Conversely, the Router detects changes to the URL — say, pressing the
"Back" button — and can tell your application exactly where you are now.

Backbone.Events

Events 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:

    var object = {};

    _.extend(object, Backbone.Events);

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

    object.trigger("alert", "an event");

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

onobject.on(event, callback, [context])Alias: bind
Bind a callback function to an object. The callback will be invoked
whenever the event is fired. If you have a large number of different
events on a page, the convention is to use colons to namespace them:
"poll:start", or "change:selection". The event string may also be a
space-delimited list of several events...

    book.on("change:title change:author", ...);

Callbacks bound to the special "all" 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:

    proxy.on("all", function(eventName) {
      object.trigger(eventName);
    });

All Backbone event methods also support an event map syntax, as an
alternative to positional arguments:

    book.on({
      "change:author": authorPane.update,
      "change:title change:subtitle": titleView.update,
      "destroy": bookView.remove
    });

To supply a context value for this when the callback is invoked, pass
the optional last argument: model.on('change', this.render, this) or
model.on({change: this.render}, this).

offobject.off([event], [callback], [context])Alias: unbind
Remove a previously-bound callback function from an object. If no
context is specified, all of the versions of the callback with different
contexts will be removed. If no callback is specified, all callbacks for
the event will be removed. If no event is specified, callbacks for all
events will be removed.

    // 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();

Note that calling model.off(), for example, will indeed remove all
events on the model — including events that Backbone uses for internal
bookkeeping.

triggerobject.trigger(event, [*args])
Trigger callbacks for the given event, or space-delimited list of
events. Subsequent arguments to trigger will be passed along to the
event callbacks.

onceobject.once(event, callback, [context])
Just like on, but causes the bound callback to fire only once before
being removed. Handy for saying "the next time that X happens, do this".
When multiple events are passed in using the space separated syntax, the
event will fire once for every event you passed in, not once for a
combination of all events

listenToobject.listenTo(other, event, callback)
Tell an object to listen to a particular event on an other object. The
advantage of using this form, instead of
other.on(event, callback, object), is that listenTo allows the object to
keep track of the events, and they can be removed all at once later on.
The callback will always be called with object as context.

    view.listenTo(model, 'change', view.render);

stopListeningobject.stopListening([other], [event], [callback])
Tell an object to stop listening to events. Either call stopListening
with no arguments to have the object remove all of its registered
callbacks ... or be more precise by telling it to remove just the events
it's listening to on a specific object, or a specific event, or just a
specific callback.

    view.stopListening();

    view.stopListening(model);

listenToOnceobject.listenToOnce(other, event, callback)
Just like listenTo, but causes the bound callback to fire only once
before being removed.

Catalog of Events
Here's the complete list of built-in Backbone events, with arguments.
You're also free to trigger your own events on Models, Collections and
Views as you see fit. The Backbone object itself mixes in Events, and
can be used to emit any global events that your application needs.

-   "add" (model, collection, options) — when a model is added to a
    collection.
-   "remove" (model, collection, options) — when a model is removed from
    a collection.
-   "update" (collection, options) — single event triggered after any
    number of models have been added, removed or changed in a
    collection.
-   "reset" (collection, options) — when the collection's entire
    contents have been reset.
-   "sort" (collection, options) — when the collection has been
    re-sorted.
-   "change" (model, options) — when a model's attributes have changed.
-   "changeId" (model, previousId, options) — when the model's id has
    been updated.
-   "change:[attribute]" (model, value, options) — when a specific
    attribute has been updated.
-   "destroy" (model, collection, options) — when a model is destroyed.
-   "request" (model_or_collection, xhr, options) — when a model or
    collection has started a request to the server.
-   "sync" (model_or_collection, response, options) — when a model or
    collection has been successfully synced with the server.
-   "error" (model_or_collection, xhr, options) — when a model's or
    collection's request to the server has failed.
-   "invalid" (model, error, options) — when a model's validation fails
    on the client.
-   "route:[name]" (params) — Fired by the router when a specific route
    is matched.
-   "route" (route, params) — Fired by the router when any route has
    been matched.
-   "route" (router, route, params) — Fired by history when any route
    has been matched.
-   "all" — this special event fires for any triggered event, passing
    the event name as the first argument followed by all trigger
    arguments.

Generally speaking, when calling a function that emits an event
(model.set, collection.add, and so on...), if you'd like to prevent the
event from being triggered, you may pass {silent: true} as an option.
Note that this is rarely, perhaps even never, a good idea. Passing
through a specific flag in the options for your event callback to look
at, and choose to ignore, will usually work out better.

Backbone.Model

Models 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 Backbone.Model with your domain-specific methods, and Model
provides a basic set of functionality for managing changes.

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, sidebar will be available in your browser's console, so you can
play around with it.

    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();

extendBackbone.Model.extend(properties, [classProperties])
To create a Model class of your own, you extend Backbone.Model and
provide instance properties, as well as optional classProperties to be
attached directly to the constructor function.

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

    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);
      }

    });

Brief aside on super: JavaScript does not provide a simple way to call
super — the function of the same name defined higher on the prototype
chain. If you override a core function like set, or save, and you want
to invoke the parent object's implementation, you'll have to explicitly
call it, along these lines:

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

preinitializenew Model([attributes], [options])
For use with models as ES classes. If you define a preinitialize method,
it will be invoked when the Model is first created, before any
instantiation logic is run for the Model.

    class Country extends Backbone.Model {
        preinitialize({countryCode}) {
          this.name = COUNTRY_NAMES[countryCode];
        }

        initialize() { ... }
    }

constructor / initializenew Model([attributes], [options])
When creating an instance of a model, you can pass in the initial values
of the attributes, which will be set on the model. If you define an
initialize function, it will be invoked when the model is created.

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

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

    var Library = Backbone.Model.extend({
      constructor: function() {
        this.books = new Books();
        Backbone.Model.apply(this, arguments);
      },
      parse: function(data, options) {
        this.books.reset(data.books);
        return data.library;
      }
    });

If you pass a {collection: ...} as the options, the model gains a
collection property that will be used to indicate which collection the
model belongs to, and is used to help compute the model's url. The
model.collection property is normally created automatically when you
first add a model to a collection. Note that the reverse is not true, as
passing this option to the constructor will not automatically add the
model to the collection. Useful, sometimes.

If {parse: true} is passed as an option, the attributes will first be
converted by parse before being set on the model.

getmodel.get(attribute)
Get the current value of an attribute from the model. For example:
note.get("title")

setmodel.set(attributes, [options])
Set a hash of attributes (one or many) on the model. If any of the
attributes change the model's state, a "change" event will be triggered
on the model. Change events for specific attributes are also triggered,
and you can bind to those as well, for example: change:title, and
change:content. You may also pass individual keys and values.

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

    book.set("title", "A Scandal in Bohemia");

escapemodel.escape(attribute)
Similar to get, but returns the HTML-escaped version of a model's
attribute. If you're interpolating data from the model into HTML, using
escape to retrieve attributes will prevent XSS attacks.

    var hacker = new Backbone.Model({
      name: "<script>alert('xss')</script>"
    });

    alert(hacker.escape('name'));

hasmodel.has(attribute)
Returns true if the attribute is set to a non-null or non-undefined
value.

    if (note.has("title")) {
      ...
    }

unsetmodel.unset(attribute, [options])
Remove an attribute by deleting it from the internal attributes hash.
Fires a "change" event unless silent is passed as an option.

clearmodel.clear([options])
Removes all attributes from the model, including the id attribute. Fires
a "change" event unless silent is passed as an option.

idmodel.id
A special property of models, the id is an arbitrary string (integer id
or UUID). If you set the id in the attributes hash, it will be copied
onto the model as a direct property. model.id should not be manipulated
directly, it should be modified only via model.set('id', …). Models can
be retrieved by id from collections, and the id is used to generate
model URLs by default.

idAttributemodel.idAttribute
A model's unique identifier is stored under the id attribute. If you're
directly communicating with a backend (CouchDB, MongoDB) that uses a
different unique key, you may set a Model's idAttribute to transparently
map from that key to id.

    var Meal = Backbone.Model.extend({
      idAttribute: "_id"
    });

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

cidmodel.cid
A special property of models, the cid 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 id, but already
needs to be visible in the UI.

attributesmodel.attributes
The attributes property is the internal hash containing the model's
state — 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.

Please use set to update the attributes instead of modifying them
directly. If you'd like to retrieve and munge a copy of the model's
attributes, use _.clone(model.attributes) instead.

Due to the fact that Events accepts space separated lists of events,
attribute names should not include spaces.

changedmodel.changed
The changed property is the internal hash containing all the attributes
that have changed since its last set. Please do not update changed
directly since its state is internally maintained by set. A copy of
changed can be acquired from changedAttributes.

defaultsmodel.defaults or model.defaults()
The defaults 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.

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

    alert("Dessert will be " + (new Meal).get('dessert'));

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 defaults as a function.

toJSONmodel.toJSON([options])
Return a shallow copy of the model's attributes for JSON
stringification. This can be used for persistence, serialization, or for
augmentation before being sent to the server. The name of this method is
a bit confusing, as it doesn't actually return a JSON string — but I'm
afraid that it's the way that the JavaScript API for JSON.stringify
works.

    var artist = new Backbone.Model({
      firstName: "Wassily",
      lastName: "Kandinsky"
    });

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

    alert(JSON.stringify(artist));

syncmodel.sync(method, model, [options])
Uses Backbone.sync to persist the state of a model to the server. Can be
overridden for custom behavior.

fetchmodel.fetch([options])
Merges the model's state with attributes fetched from the server by
delegating to Backbone.sync. Returns a jqXHR. Useful if the model has
never been populated with data, or if you'd like to ensure that you have
the latest server state. Triggers a "change" event if the server's state
differs from the current attributes. fetch accepts success and error
callbacks in the options hash, which are both passed
(model, response, options) as arguments.

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

savemodel.save([attributes], [options])
Save a model to your database (or alternative persistence layer), by
delegating to Backbone.sync. Returns a jqXHR if validation is successful
and false otherwise. The attributes hash (as in set) should contain the
attributes you'd like to change — keys that aren't mentioned won't be
altered — but, a complete representation of the resource will be sent to
the server. As with set, you may pass individual keys and values instead
of a hash. If the model has a validate method, and validation fails, the
model will not be saved. If the model isNew, the save will be a "create"
(HTTP POST), if the model already exists on the server, the save will be
an "update" (HTTP PUT).

If instead, you'd only like the changed attributes to be sent to the
server, call model.save(attrs, {patch: true}). You'll get an HTTP PATCH
request to the server with just the passed-in attributes.

Calling save with new attributes will cause a "change" event
immediately, a "request" event as the Ajax request begins to go to the
server, and a "sync" event after the server has acknowledged the
successful change. Pass {wait: true} if you'd like to wait for the
server before setting the new attributes on the model.

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

    Backbone.sync = function(method, model) {
      alert(method + ": " + JSON.stringify(model));
      model.set('id', 1);
    };

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

    book.save();

    book.save({author: "Teddy"});

save accepts success and error callbacks in the options hash, which will
be passed the arguments (model, response, options). If a server-side
validation fails, return a non-200 HTTP response code, along with an
error response in text or JSON.

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

destroymodel.destroy([options])
Destroys the model on the server by delegating an HTTP DELETE request to
Backbone.sync. Returns a jqXHR object, or false if the model isNew.
Accepts success and error callbacks in the options hash, which will be
passed (model, response, options). Triggers a "destroy" event on the
model, which will bubble up through any collections that contain it, a
"request" event as it begins the Ajax request to the server, and a
"sync" event, after the server has successfully acknowledged the model's
deletion. Pass {wait: true} if you'd like to wait for the server to
respond before removing the model from the collection.

    book.destroy({success: function(model, response) {
      ...
    }});

Underscore Methods (9)
Backbone proxies to Underscore.js to provide 9 object functions on
Backbone.Model. They aren't all documented here, but you can take a look
at the Underscore documentation for the full details…

-   keys
-   values
-   pairs
-   invert
-   pick
-   omit
-   chain
-   isEmpty

    user.pick('first_name', 'last_name', 'email');

    chapters.keys().join(', ');

validatemodel.validate(attributes, options)
This method is left undefined and you're encouraged to override it with
any custom validation logic you have that can be performed in
JavaScript. If the attributes are valid, don't return anything from
validate; 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.

By default save checks validate before setting any attributes but you
may also tell set to validate the new attributes by passing
{validate: true} as an option. The validate method receives the model
attributes as well as any options passed to set or save, if validate
returns an error, save does not continue, the model attributes are not
modified on the server, an "invalid" event is triggered, and the
validationError property is set on the model with the value returned by
this method.

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

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

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

    one.save({
      start: 15,
      end:   10
    });

"invalid" events are useful for providing coarse-grained error messages
at the model or collection level.

validationErrormodel.validationError
The value returned by validate during the last failed validation.

isValidmodel.isValid(options)
Run validate to check the model state.

The validate method receives the model attributes as well as any options
passed to isValid, if validate returns an error an "invalid" event is
triggered, and the error is set on the model in the validationError
property.

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

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

    one.set({
      start: 15,
      end:   10
    });

    if (!one.isValid()) {
      alert(one.get("title") + " " + one.validationError);
    }

urlmodel.url()
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:
"[collection.url]/[id]" by default, but you may override by specifying
an explicit urlRoot if the model's collection shouldn't be taken into
account.

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

urlRootmodel.urlRoot or model.urlRoot()
Specify a urlRoot if you're using a model outside of a collection, to
enable the default url function to generate URLs based on the model id.
"[urlRoot]/id"
Normally, you won't need to define this. Note that urlRoot may also be a
function.

    var Book = Backbone.Model.extend({urlRoot : '/books'});

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

    alert(solaris.url());

parsemodel.parse(response, options)
parse is called whenever a model's data is returned by the server, in
fetch, and save. The function is passed the raw response object, and
should return the attributes hash to be set 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.

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

    ActiveRecord::Base.include_root_in_json = false

clonemodel.clone()
Returns a new instance of the model with identical attributes.

isNewmodel.isNew()
Has this model been saved to the server yet? If the model does not yet
have an id, it is considered to be new.

hasChangedmodel.hasChanged([attribute])
Has the model changed since its last set? If an attribute is passed,
returns true if that specific attribute has changed.

Note that this method, and the following change-related ones, are only
useful during the course of a "change" event.

    book.on("change", function() {
      if (book.hasChanged("title")) {
        ...
      }
    });

changedAttributesmodel.changedAttributes([attributes])
Retrieve a hash of only the model's attributes that have changed since
the last set, or false if there are none. Optionally, an external
attributes 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.

previousmodel.previous(attribute)
During a "change" event, this method can be used to get the previous
value of a changed attribute.

    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"});

previousAttributesmodel.previousAttributes()
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.

Backbone.Collection

Collections are ordered sets of models. You can bind "change" events to
be notified when any model in the collection has been modified, listen
for "add" and "remove" events, fetch the collection from the server, and
use a full suite of Underscore.js methods.

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: documents.on("change:selected", ...)

extendBackbone.Collection.extend(properties, [classProperties])
To create a Collection class of your own, extend Backbone.Collection,
providing instance properties, as well as optional classProperties to be
attached directly to the collection's constructor function.

modelcollection.model([attrs], [options])
Override this property to specify the model class that the collection
contains. If defined, you can pass raw attributes objects (and arrays)
and options to add, create, and reset, and the attributes will be
converted into a model of the proper type using the provided options, if
any.

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

A collection can also contain polymorphic models by overriding this
property with a constructor that returns a model.

    var Library = Backbone.Collection.extend({

      model: function(attrs, options) {
        if (condition) {
          return new PublicDocument(attrs, options);
        } else {
          return new PrivateDocument(attrs, options);
        }
      }

    });

modelIdcollection.modelId(attrs, idAttribute)
Override this method to return the value the collection will use to
identify a model given its attributes. Useful for combining models from
multiple tables with different idAttribute values into a single
collection.

By default returns the value of the given idAttribute within the attrs,
or failing that, id. If your collection uses a model factory and the id
ranges of those models might collide, you must override this method.

    var Library = Backbone.Collection.extend({
      modelId: function(attrs) {
        return attrs.type + attrs.id;
      }
    });

    var library = new Library([
      {type: 'dvd', id: 1},
      {type: 'vhs', id: 1}
    ]);

    var dvdId = library.get('dvd1').id;
    var vhsId = library.get('vhs1').id;
    alert('dvd: ' + dvdId + ', vhs: ' + vhsId);

preinitializenew Backbone.Collection([models], [options])
For use with collections as ES classes. If you define a preinitialize
method, it will be invoked when the Collection is first created and
before any instantiation logic is run for the Collection.

    class Library extends Backbone.Collection {
      preinitialize() {
        this.on("add", function() {
          console.log("Add model event got fired!");
        });
      }
    }

constructor / initializenew Backbone.Collection([models], [options])
When creating a Collection, you may choose to pass in the initial array
of models. The collection's comparator may be included as an option.
Passing false as the comparator option will prevent sorting. If you
define an initialize function, it will be invoked when the collection is
created. There are a couple of options that, if provided, are attached
to the collection directly: model and comparator.
Pass null for models to create an empty Collection with options.

    var tabs = new TabSet([tab1, tab2, tab3]);
    var spaces = new Backbone.Collection(null, {
      model: Space
    });

modelscollection.models
Raw access to the JavaScript array of models inside of the collection.
Usually you'll want to use get, at, or the Underscore methods to access
model objects, but occasionally a direct reference to the array is
desired.

toJSONcollection.toJSON([options])
Return an array containing the attributes hash of each model (via
toJSON) 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 JavaScript's JSON API.

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

    alert(JSON.stringify(collection));

synccollection.sync(method, collection, [options])
Uses Backbone.sync to persist the state of a collection to the server.
Can be overridden for custom behavior.

Underscore Methods (46)
Backbone proxies to Underscore.js to provide 46 iteration functions on
Backbone.Collection. They aren't all documented here, but you can take a
look at the Underscore documentation for the full details…

Most methods can take an object or string to support
model-attribute-style predicates or a function that receives the model
instance as an argument.

-   forEach (each)
-   map (collect)
-   reduce (foldl, inject)
-   reduceRight (foldr)
-   find (detect)
-   findIndex
-   findLastIndex
-   filter (select)
-   reject
-   every (all)
-   some (any)
-   contains (includes)
-   invoke
-   max
-   min
-   sortBy
-   groupBy
-   shuffle
-   toArray
-   size
-   first (head, take)
-   initial
-   rest (tail, drop)
-   last
-   without
-   indexOf
-   lastIndexOf
-   isEmpty
-   chain
-   difference
-   sample
-   partition
-   countBy
-   indexBy

    books.each(function(book) {
      book.publish();
    });

    var titles = books.map("title");

    var publishedBooks = books.filter({published: true});

    var alphabetical = books.sortBy(function(book) {
      return book.author.get("name").toLowerCase();
    });

    var randomThree = books.sample(3);

addcollection.add(models, [options])
Add a model (or an array of models) to the collection, firing an "add"
event for each model, and an "update" event afterwards. If a model
property is defined, you may also pass raw attributes objects and
options, and have them be vivified as instances of the model using the
provided options. Returns the added (or preexisting, if duplicate)
models. Pass {at: index} to splice the model into the collection at the
specified index. If you're adding models to the collection that are
already in the collection, they'll be ignored, unless you pass
{merge: true}, in which case their attributes will be merged into the
corresponding models, firing any appropriate "change" events.

    var ships = new Backbone.Collection;

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

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

Note that adding the same model (a model with the same id) to a
collection more than once
is a no-op.

removecollection.remove(models, [options])
Remove a model (or an array of models) from the collection, and return
them. Each model can be a Model instance, an id string or a JS object,
any value acceptable as the id argument of collection.get. Fires a
"remove" event for each model, and a single "update" event afterwards,
unless {silent: true} is passed. The model's index before removal is
available to listeners as options.index.

resetcollection.reset([models], [options])
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 reset to replace a collection with a
new list of models (or attribute hashes), triggering a single "reset"
event on completion, and without triggering any add or remove events on
any models. Returns the newly-set models. For convenience, within a
"reset" event, the list of any previous models is available as
options.previousModels.
Pass null for models to empty your Collection with options.

Here's an example using reset to bootstrap a collection during initial
page load, in a Rails application:

    <script>
      var accounts = new Backbone.Collection;
      accounts.reset(<%= @accounts.to_json %>);
    </script>

Calling collection.reset() without passing any models as arguments will
empty the entire collection.

setcollection.set(models, [options])
The set method performs a "smart" update of the collection with the
passed list of models. If a model in the list isn't yet in the
collection it will be added; if the model is already in the collection
its attributes will be merged; and if the collection contains any models
that aren't present in the list, they'll be removed. All of the
appropriate "add", "remove", and "change" events are fired as this
happens. Returns the touched models in the collection. If you'd like to
customize the behavior, you can disable it with options: {add: false},
{remove: false}, or {merge: false}.

    var vanHalen = new Backbone.Collection([eddie, alex, stone, roth]);

    vanHalen.set([eddie, alex, stone, hagar]);

    // Fires a "remove" event for roth, and an "add" event for "hagar".
    // Updates any of stone, alex, and eddie's attributes that may have
    // changed over the years.

getcollection.get(id)
Get a model from a collection, specified by an id, a cid, or by passing
in a model.

    var book = library.get(110);

atcollection.at(index)
Get a model from a collection, specified by index. Useful if your
collection is sorted, and if your collection isn't sorted, at will still
retrieve models in insertion order. When passed a negative index, it
will retrieve the model from the back of the collection.

pushcollection.push(model, [options])
Add a model at the end of a collection. Takes the same options as add.

popcollection.pop([options])
Remove and return the last model from a collection. Takes the same
options as remove.

unshiftcollection.unshift(model, [options])
Add a model at the beginning of a collection. Takes the same options as
add.

shiftcollection.shift([options])
Remove and return the first model from a collection. Takes the same
options as remove.

slicecollection.slice(begin, end)
Return a shallow copy of this collection's models, using the same
options as native Array#slice.

lengthcollection.length
Like an array, a Collection maintains a length property, counting the
number of models it contains.

comparatorcollection.comparator
By default there is no comparator for a collection. If you define a
comparator, it will be used to sort the collection any time a model is
added. A comparator can be defined as a sortBy (pass a function that
takes a single argument), as a sort (pass a comparator function that
expects two arguments), or as a string indicating the attribute to sort
by.

"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 -1 if the first
model should come before the second, 0 if they are of the same rank and
1 if the first model should come after. Note that Backbone depends on
the arity of your comparator function to determine between the two
styles, so be careful if your comparator function is bound.

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

    var Chapter  = Backbone.Model;
    var chapters = new Backbone.Collection;

    chapters.comparator = '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'));

Collections with a comparator will not automatically re-sort if you
later change model attributes, so you may wish to call sort after
changing model attributes that would affect the order.

sortcollection.sort([options])
Force a collection to re-sort itself. Note that a collection with a
comparator will sort itself automatically whenever a model is added. To
disable sorting when adding a model, pass {sort: false} to add. Calling
sort triggers a "sort" event on the collection.

pluckcollection.pluck(attribute)
Pluck an attribute from each model in the collection. Equivalent to
calling map and returning a single attribute from the iterator.

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

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

    alert(JSON.stringify(names));

wherecollection.where(attributes)
Return an array of all the models in a collection that match the passed
attributes. Useful for simple cases of filter.

    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);

findWherecollection.findWhere(attributes)
Just like where, but directly returns only the first model in the
collection that matches the passed attributes. If no model matches
returns undefined.

urlcollection.url or collection.url()
Set the url property (or function) on a collection to reference its
location on the server. Models within the collection will use url to
construct URLs of their own.

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

    // Or, something more sophisticated:

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

parsecollection.parse(response, options)
parse is called by Backbone whenever a collection's models are returned
by the server, in fetch. The function is passed the raw response object,
and should return the array of model attributes to be added 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.

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

clonecollection.clone()
Returns a new instance of the collection with an identical list of
models.

fetchcollection.fetch([options])
Fetch the default set of models for this collection from the server,
setting them on the collection when they arrive. The options hash takes
success and error callbacks which will both be passed
(collection, response, options) as arguments. When the model data
returns from the server, it uses set to (intelligently) merge the
fetched models, unless you pass {reset: true}, in which case the
collection will be (efficiently) reset. Delegates to Backbone.sync under
the covers for custom persistence strategies and returns a jqXHR. The
server handler for fetch requests should return a JSON array of models.

    Backbone.sync = function(method, model) {
      alert(method + ": " + model.url);
    };

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

    accounts.fetch();

The behavior of fetch can be customized by using the available set
options. For example, to fetch a collection, getting an "add" event for
every new model, and a "change" event for every changed existing model,
without removing anything: collection.fetch({remove: false})

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

Note that fetch should not be used to populate collections on page load
— all models needed at load time should already be bootstrapped in to
place. fetch 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.

createcollection.create(attributes, [options])
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 new model. If client-side validation
failed, the model will be unsaved, with validation errors. In order for
this to work, you should set the model property of the collection. The
create method can accept either an attributes hash and options to be
passed down during model instantiation or an existing, unsaved model
object.

Creating a model will cause an immediate "add" event to be triggered on
the collection, a "request" event as the new model is sent to the
server, as well as a "sync" event, once the server has responded with
the successful creation of the model. Pass {wait: true} if you'd like to
wait for the server before adding the new model to the collection.

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

    var nypl = new Library;

    var othello = nypl.create({
      title: "Othello",
      author: "William Shakespeare"
    });

mixinBackbone.Collection.mixin(properties)
mixin provides a way to enhance the base Backbone.Collection and any
collections which extend it. This can be used to add generic methods
(e.g. additional Underscore Methods).

    Backbone.Collection.mixin({
      sum: function(models, iteratee) {
        return _.reduce(models, function(s, m) {
          return s + iteratee(m);
        }, 0);
      }
    });

    var cart = new Backbone.Collection([
      {price: 16, name: 'monopoly'},
      {price: 5, name: 'deck of cards'},
      {price: 20, name: 'chess'}
    ]);

    var cost = cart.sum('price');

Backbone.Router

Web applications often provide linkable, bookmarkable, shareable URLs
for important locations in the app. Until recently, hash fragments
(#page) were used to provide these permalinks, but with the arrival of
the History API, it's now possible to use standard URLs (/page).
Backbone.Router 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.

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

extendBackbone.Router.extend(properties, [classProperties])
Get started by creating a custom router class. Define action functions
that are triggered when certain URL fragments are matched, and provide a
routes hash that pairs routes to actions. Note that you'll want to avoid
using a leading slash in your route definitions:

    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) {
        ...
      }

    });

routesrouter.routes
The routes hash maps URLs with parameters to functions on your router
(or just direct function definitions, if you prefer), similar to the
View's events hash. Routes can contain parameter parts, :param, which
match a single URL component between slashes; and splat parts *splat,
which can match any number of URL components. Part of a route can be
made optional by surrounding it in parentheses (/:optional).

For example, a route of "search/:query/p:page" will match a fragment of
#search/obama/p2, passing "obama" and "2" to the action as positional
arguments.

A route of "file/*path" will match #file/folder/file.txt, passing
"folder/file.txt" to the action.

A route of "docs/:section(/:subsection)" will match #docs/faq and
#docs/faq/installing, passing "faq" to the action in the first case, and
passing "faq" and "installing" to the action in the second.

A nested optional route of "docs(/:section)(/:subsection)" will match
#docs, #docs/faq, and #docs/faq/installing, passing "faq" to the action
in the second case, and passing "faq" and "installing" to the action in
the third.

Trailing slashes are treated as part of the URL, and (correctly) treated
as a unique route when accessed. docs and docs/ will fire different
callbacks. If you can't avoid generating both types of URLs, you can
define a "docs(/)" matcher to capture both cases.

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
event, so that other objects can listen to the router, and be notified.
In the following example, visiting #help/uploading will fire a
route:help event from the router.

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

    router.on("route:help", function(page) {
      ...
    });

preinitializenew Backbone.Router([options])
For use with routers as ES classes. If you define a preinitialize
method, it will be invoked when the Router is first created and before
any instantiation logic is run for the Router.

    class Router extends Backbone.Router {
      preinitialize() {
        // Override execute method
        this.execute = function(callback, args, name) {
          if (!loggedIn) {
            goToLogin();
            return false;
          }
          args.push(parseQueryString(args.pop()));
          if (callback) callback.apply(this, args);
        }
      }
    }

constructor / initializenew Router([options])
When creating a new router, you may pass its routes hash directly as an
option, if you choose. All options will also be passed to your
initialize function, if defined.

routerouter.route(route, name, [callback])
Manually create a route for the router, The route argument may be a
routing string or regular expression. Each matching capture from the
route or regular expression will be passed as an argument to the
callback. The name argument will be triggered as a "route:name" event
whenever the route is matched. If the callback argument is omitted
router[name] will be used instead. Routes added later may override
previously declared routes.

    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) { ... }

navigaterouter.navigate(fragment, [options])
Whenever you reach a point in your application that you'd like to save
as a URL, call navigate in order to update the URL. If you also wish to
call the route function, set the trigger option to true. To update the
URL without creating an entry in the browser's history, set the replace
option to true.

    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});

executerouter.execute(callback, args, name)
This method is called internally within the router, whenever a route
matches and its corresponding callback is about to be executed. Return
false from execute to cancel the current transition. Override it to
perform custom parsing or wrapping of your routes, for example, to parse
query strings before handing them to your route callback, like so:

    var Router = Backbone.Router.extend({
      execute: function(callback, args, name) {
        if (!loggedIn) {
          goToLogin();
          return false;
        }
        args.push(parseQueryString(args.pop()));
        if (callback) callback.apply(this, args);
      }
    });

Backbone.history

History serves as a global router (per frame) to handle hashchange
events or pushState, match the appropriate route, and trigger callbacks.
You shouldn't ever have to create one of these yourself since
Backbone.history already contains one.

pushState support exists on a purely opt-in basis in Backbone. Older
browsers that don't support pushState will continue to use hash-based
URL fragments, and if a hash URL is visited by a pushState-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 /documents/100, 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.

startBackbone.history.start([options])
When all of your Routers have been created, and all of the routes are
set up properly, call Backbone.history.start() to begin monitoring
hashchange events, and dispatching routes. Subsequent calls to
Backbone.history.start() will throw an error, and
Backbone.History.started is a boolean value indicating whether it has
already been called.

To indicate that you'd like to use HTML5 pushState support in your
application, use Backbone.history.start({pushState: true}). If you'd
like to use pushState, but have browsers that don't support it natively
use full page refreshes instead, you can add {hashChange: false} to the
options.

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

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

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

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

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

Backbone.sync

Backbone.sync is the function that Backbone calls every time it attempts
to read or save a model to the server. By default, it uses jQuery.ajax
to make a RESTful JSON request and returns a jqXHR. You can override it
in order to use a different persistence strategy, such as WebSockets,
XML transport, or Local Storage.

The method signature of Backbone.sync is sync(method, model, [options])

-   method – the CRUD method ("create", "read", "update", or "delete")
-   model – the model to be saved (or collection to be read)
-   options – success and error callbacks, and all other jQuery request
    options

With the default implementation, when Backbone.sync 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 application/json. 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 "read" request from a collection (Collection#fetch),
send down an array of model attribute objects.

Whenever a model or collection begins a sync with the server, a
"request" event is emitted. If the request completes successfully you'll
get a "sync" event, and an "error" event if not.

The sync function may be overridden globally as Backbone.sync, or at a
finer-grained level, by adding a sync function to a Backbone collection
or to an individual model.

The default sync handler maps CRUD to REST like so:

-   create → POST   /collection
-   read → GET   /collection[/id]
-   update → PUT   /collection/id
-   patch → PATCH   /collection/id
-   delete → DELETE   /collection/id

As an example, a Rails 4 handler responding to an "update" call from
Backbone might look like this:

    def update
      account = Account.find params[:id]
      permitted = params.require(:account).permit(:name, :otherparam)
      account.update_attributes permitted
      render :json => account
    end

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

ajaxBackbone.ajax = function(request) { ... };
If you want to use a custom AJAX function, or your endpoint doesn't
support the jQuery.ajax API and you need to tweak things, you can do so
by setting Backbone.ajax.

emulateHTTPBackbone.emulateHTTP = true
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
Backbone.emulateHTTP. Setting this option will fake PUT, PATCH and
DELETE requests with a HTTP POST, setting the X-HTTP-Method-Override
header with the true method. If emulateJSON is also on, the true method
will be passed as an additional _method parameter.

    Backbone.emulateHTTP = true;

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

emulateJSONBackbone.emulateJSON = true
If you're working with a legacy web server that can't handle requests
encoded as application/json, setting Backbone.emulateJSON = true; will
cause the JSON to be serialized under a model parameter, and the request
to be made with a application/x-www-form-urlencoded MIME type, as if
from an HTML form.

Backbone.View

Backbone views are almost more convention than they are code — 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 render function to the model's "change" event — and now
everywhere that model data is displayed in the UI, it is always
immediately up to date.

extendBackbone.View.extend(properties, [classProperties])
Get started with views by creating a custom view class. You'll want to
override the render function, specify your declarative events, and
perhaps the tagName, className, or id of the View's root element.

    var DocumentRow = Backbone.View.extend({

      tagName: "li",

      className: "document-row",

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

      initialize: function() {
        this.listenTo(this.model, "change", this.render);
      },

      render: function() {
        ...
      }

    });

Properties like tagName, id, className, el, and events may also be
defined as a function, if you want to wait to define them until runtime.

preinitializenew View([options])
For use with views as ES classes. If you define a preinitialize method,
it will be invoked when the view is first created, before any
instantiation logic is run.

    class Document extends Backbone.View {
      preinitialize({autoRender}) {
        this.autoRender = autoRender;
      }

      initialize() {
        if (this.autoRender) {
          this.listenTo(this.model, "change", this.render);
        }
      }
    }

constructor / initializenew View([options])
There are several special options that, if passed, will be attached
directly to the view: model, collection, el, id, className, tagName,
attributes and events. If the view defines an initialize function, it
will be called when the view is first created. If you'd like to create a
view that references an element already in the DOM, pass in the element
as an option: new View({el: existingElement})

    var doc = documents.first();

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

elview.el
All views have a DOM element at all times (the el 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.

this.el can be resolved from a DOM selector string or an Element;
otherwise it will be created from the view's tagName, className, id and
attributes properties. If none are set, this.el is an empty div, which
is often just fine. An el reference may also be passed in to the view's
constructor.

    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);

$elview.$el
A cached jQuery object for the view's element. A handy reference instead
of re-wrapping the DOM element all the time.

    view.$el.show();

    listView.$el.append(itemView.el);

setElementview.setElement(element)
If you'd like to apply a Backbone view to a different DOM element, use
setElement, which will also create the cached $el reference and move the
view's delegated events from the old element to the new one.

attributesview.attributes
A hash of attributes that will be set as HTML DOM element attributes on
the view's el (id, class, data-properties, etc.), or a function that
returns such a hash.

$ (jQuery)view.$(selector)
If jQuery is included on the page, each view has a $ 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: view.$el.find(selector)

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

templateview.template([data])
While templating for a view isn't a function provided directly by
Backbone, it's often a nice convention to define a template function on
your views. In this way, when rendering your view, you have convenient
access to instance data. For example, using Underscore templates:

    var LibraryView = Backbone.View.extend({
      template: _.template(...)
    });

renderview.render()
The default implementation of render is a no-op. Override this function
with your code that renders the view template from model data, and
updates this.el with the new HTML. A good convention is to return this
at the end of render to enable chained calls.

    var Bookmark = Backbone.View.extend({
      template: _.template(...),
      render: function() {
        this.$el.html(this.template(this.model.attributes));
        return this;
      }
    });

Backbone is agnostic with respect to your preferred method of HTML
templating. Your render function could even munge together an HTML
string, or use document.createElement to generate a DOM tree. However,
we suggest choosing a nice JavaScript templating library. Mustache.js,
Haml-js, and Eco are all fine alternatives. Because Underscore.js is
already on the page, _.template is available, and is an excellent choice
if you prefer simple interpolated-JavaScript style templates.

Whatever templating strategy you end up with, it's nice if you never
have to put strings of HTML in your JavaScript. At DocumentCloud, we use
Jammit in order to package up JavaScript templates stored in /app/views
as part of our main core.js asset package.

removeview.remove()
Removes a view and its el from the DOM, and calls stopListening to
remove any bound events that the view has listenTo'd.

eventsview.events or view.events()
The events hash (or method) can be used to specify a set of DOM events
that will be bound to methods on your View through delegateEvents.

Backbone will automatically attach the event listeners at instantiation
time, right before invoking initialize.

    var ENTER_KEY = 13;
    var InputView = Backbone.View.extend({

      tagName: 'input',

      events: {
        "keydown" : "keyAction",
      },

      render: function() { ... },

      keyAction: function(e) {
        if (e.which === ENTER_KEY) {
          this.collection.add({text: this.$el.val()});
        }
      }
    });

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

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

Using delegateEvents provides a number of advantages over manually using
jQuery to bind events to child elements during render. All attached
callbacks are bound to the view before being handed off to jQuery, so
when the callbacks are invoked, this continues to refer to the view
object. When delegateEvents is run again, perhaps with a different
events hash, all callbacks are removed and delegated afresh — useful for
views which need to behave differently when in different modes.

A single-event version of delegateEvents is available as delegate. In
fact, delegateEvents is simply a multi-event wrapper around delegate. A
counterpart to undelegateEvents is available as undelegate.

A view that displays a document in a search result might look something
like this:

    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.attributes));
        return this;
      },

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

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

      ...

    });

undelegateEventsundelegateEvents()
Removes all of the view's delegated events. Useful if you want to
disable or remove a view from the DOM temporarily.

Utility

Backbone.noConflictvar backbone = Backbone.noConflict();
Returns the Backbone object back to its original value. You can use the
return value of Backbone.noConflict() 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.

    var localBackbone = Backbone.noConflict();
    var model = localBackbone.Model.extend(...);

Backbone.$Backbone.$ = $;
If you have multiple copies of jQuery 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.

    Backbone.$ = require('jquery');

F.A.Q.

Why use Backbone, not [other framework X]?
If your eye hasn't already been caught by the adaptability and elan on
display in the above list of examples, we can get more specific:
Backbone.js aims to provide the common foundation that data-rich web
applications with ambitious interfaces require — while very deliberately
avoiding painting you into a corner by making any decisions that you're
better equipped to make yourself.

-   The focus is on supplying you with helpful methods to manipulate and
    query your data, not on HTML widgets or reinventing the JavaScript
    object model.
-   Backbone does not force you to use a single template engine. Views
    can bind to HTML constructed in your favorite way.
-   It's smaller. There are fewer kilobytes for your browser or phone to
    download, and less conceptual surface area. You can read and
    understand the source in an afternoon.
-   It doesn't depend on stuffing application logic into your HTML.
    There's no embedded JavaScript, template logic, or binding hookup
    code in data- or ng- attributes, and no need to invent your own HTML
    tags.
-   Synchronous events are used as the fundamental building block, not a
    difficult-to-reason-about run loop, or by constantly polling and
    traversing your data structures to hunt for changes. And if you want
    a specific event to be asynchronous and aggregated, no problem.
-   Backbone scales well, from embedded widgets to massive apps.
-   Backbone is a library, not a framework, and plays well with others.
    You can embed Backbone widgets in Dojo apps without trouble, or use
    Backbone models as the data backing for D3 visualizations (to pick
    two entirely random examples).
-   "Two-way data-binding" is avoided. While it certainly makes for a
    nifty demo, and works for the most basic CRUD, it doesn't tend to be
    terribly useful in your real-world app. Sometimes you want to update
    on every keypress, sometimes on blur, sometimes when the panel is
    closed, and sometimes when the "save" button is clicked. In almost
    all cases, simply serializing the form to JSON is faster and easier.
    All that aside, if your heart is set, go for it.
-   There's no built-in performance penalty for choosing to structure
    your code with Backbone. And if you do want to optimize further,
    thin models and templates with flexible granularity make it easy to
    squeeze every last drop of potential performance out of, say, IE8.

There's More Than One Way To Do It
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...

References between Models and Views can be handled several ways. Some
people like to have direct pointers, where views correspond 1:1 with
models (model.view and view.model). 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.

Batch operations 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: /notes/batch/destroy?ids=1,2,3,4. Others
tunnel REST over JSON, with the creation of "changeset" requests:

      {
        "create":  [array of models to create]
        "update":  [array of models to update]
        "destroy": [array of model ids to destroy]
      }

Feel free to define your own events. Backbone.Events 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: model.on("selected:true") or model.on("editing")

Render the UI as you see fit. Backbone is agnostic as to whether you use
Underscore templates, Mustache.js, direct DOM manipulation, server-side
rendered snippets of HTML, or jQuery UI in your render 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.

Nested Models & Collections
It's common to nest collections inside of models with Backbone. For
example, consider a Mailbox model that contains many Message models. One
nice pattern for handling this is have a this.messages collection for
each mailbox, enabling the lazy-loading of messages, when the mailbox is
first opened ... perhaps with MessageList views listening for "add" and
"remove" events.

    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({reset: true});

If you're looking for something more opinionated, there are a number of
Backbone plugins that add sophisticated associations among models,
available on the wiki.

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
Backbone should provide the foundation for implementing any of them. You
may want to…

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

Loading Bootstrapped Models
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 fetch them, a nicer pattern is to
have their data already bootstrapped into the page. You can then use
reset to populate your collections with the initial data. At
DocumentCloud, in the ERB template for the workspace, we do something
along these lines:

    <script>
      var accounts = new Backbone.Collection;
      accounts.reset(<%= @accounts.to_json %>);
      var projects = new Backbone.Collection;
      projects.reset(<%= @projects.to_json(:collaborators => true) %>);
    </script>

You have to escape </ within the JSON string, to prevent JavaScript
injection attacks.

Extending Backbone
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 not that kind of library.

Because it serves as a foundation for your application, you're meant to
extend and enhance it in the ways you see fit — the entire source code
is annotated 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
overridden or augmented should you find the need. If you catch yourself
adding methods to Backbone.Model.prototype, or creating your own base
subclass, don't worry — that's how things are supposed to work.

How does Backbone relate to "traditional" MVC?
Different implementations of the Model-View-Controller pattern tend to
disagree about the definition of a controller. If it helps any, in
Backbone, the View 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.

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

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

Binding "this"
Perhaps the single most common JavaScript "gotcha" is the fact that when
you pass a function as a callback, its value for this is lost. When
dealing with events and callbacks in Backbone, you'll often find it
useful to rely on listenTo or the optional context argument that many of
Underscore and Backbone's methods use to specify the this that will be
used when the callback is later invoked. (See _.each, _.map, and
object.on, to name a few). View events are automatically bound to the
view's context for you. You may also find it helpful to use _.bind and
_.bindAll from Underscore.js.

    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);

        messsages.each(this.addMessage, this);
      }

    });

    // Later, in the app...

    Inbox.messages.add(newMessage);

Working with Rails
Backbone.js was originally extracted from a Rails application; 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.

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:

    ActiveRecord::Base.include_root_in_json = false

... in your configuration. Otherwise, override parse 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 params, or you can override toJSON in Backbone to add the
extra wrapping Rails expects.

Examples

The list of examples that follows, while long, is not exhaustive — nor
in any way current. If you've worked on an app that uses Backbone,
please add it to the wiki page of Backbone apps.

Jérôme Gravel-Niquet has contributed a Todo List application 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 read through
the annotated source. The app uses a LocalStorage adapter to
transparently save all of your todos within your browser, instead of
sending them to a server. Jérôme also has a version hosted at
localtodos.com.

DocumentCloud

The DocumentCloud workspace is built on Backbone.js, with Documents,
Projects, Notes, and Accounts all as Backbone models and collections. If
you're interested in history — both Underscore.js and Backbone.js were
originally extracted from the DocumentCloud codebase, and packaged into
standalone JS libraries.

USA Today

USA Today takes advantage of the modularity of Backbone's data/model
lifecycle — which makes it simple to create, inherit, isolate, and link
application objects — to keep the codebase both manageable and
efficient. The new website also makes heavy use of the Backbone Router
to control the page for both pushState-capable and legacy browsers.
Finally, the team took advantage of Backbone's Event module to create a
PubSub API that allows third parties and analytics packages to hook into
the heart of the app.

Rdio

New Rdio 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 Rdio API.
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
desktop applications.

Hulu

Hulu used Backbone.js to build its next generation online video
experience. With Backbone as a foundation, the web interface was
rewritten from scratch so that all page content can be loaded
dynamically with smooth transitions as you navigate. Backbone makes it
easy to move through the app quickly without the reloading of scripts
and embedded videos, while also offering models and collections for
additional data manipulation support.

Quartz

Quartz sees itself as a digitally native news outlet for the new global
economy. Because Quartz believes in the future of open, cross-platform
web applications, they selected Backbone and Underscore to fetch, sort,
store, and display content from a custom WordPress API. Although qz.com
uses responsive design for phone, tablet, and desktop browsers, it also
takes advantage of Backbone events and views to render device-specific
templates in some cases.

Earth

Earth.nullschool.net displays real-time weather conditions on an
interactive animated globe, and Backbone provides the foundation upon
which all of the site's components are built. Despite the presence of
several other JavaScript libraries, Backbone's non-opinionated design
made it effortless to mix-in the Events functionality used for
distributing state changes throughout the page. When the decision was
made to switch to Backbone, large blocks of custom logic simply
disappeared.

Vox

Vox Media, the publisher of SB Nation, The Verge, Polygon, Eater,
Racked, Curbed, and Vox.com, uses Backbone throughout Chorus, its
home-grown publishing platform. Backbone powers the liveblogging
platform and commenting system used across all Vox Media properties;
Coverage, an internal editorial coordination tool; SB Nation Live, a
live event coverage and chat tool; and Vox Cards, Vox.com's
highlighter-and-index-card inspired app for providing context about the
news.

Gawker Media

Kinja is Gawker Media's publishing platform designed to create great
stories by breaking down the lines between the traditional roles of
content creators and consumers. Everyone — editors, readers, marketers —
have access to the same tools to engage in passionate discussion and
pursue the truth of the story. Sharing, recommending, and following
within the Kinja ecosystem allows for improved information discovery
across all the sites.

Kinja is the platform behind Gawker, Gizmodo, Lifehacker, io9 and other
Gawker Media blogs. Backbone.js underlies the front-end application code
that powers everything from user authentication to post authoring,
commenting, and even serving ads. The JavaScript stack includes
Underscore.js and jQuery, with some plugins, all loaded with RequireJS.
Closure templates are shared between the Play! Framework based Scala
application and Backbone views, and the responsive layout is done with
the Foundation framework using SASS.

Flow

MetaLab used Backbone.js to create Flow, 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 window.Flow.

Gilt Groupe

Gilt Groupe uses Backbone.js to build multiple applications across their
family of sites. Gilt's mobile website uses Backbone and Zepto.js to
create a blazing-fast shopping experience for users on-the-go, while
Gilt Live combines Backbone with WebSockets to display the items that
customers are buying in real-time. Gilt's search functionality also uses
Backbone to filter and sort products efficiently by moving those actions
to the client-side.

Enigma

Enigma is a portal amassing the largest collection of public data
produced by governments, universities, companies, and organizations.
Enigma uses Backbone Models and Collections to represent complex data
structures; and Backbone's Router gives Enigma users unique URLs for
application states, allowing them to navigate quickly through the site
while maintaining the ability to bookmark pages and navigate forward and
backward through their session.

NewsBlur

NewsBlur is an RSS feed reader and social news network with a fast and
responsive UI that feels like a native desktop app. Backbone.js was
selected for a major rewrite and transition from spaghetti code because
of its powerful yet simple feature set, easy integration, and large
community. If you want to poke around under the hood, NewsBlur is also
entirely open-source.

WordPress.com

WordPress.com is the software-as-a-service version of WordPress. It uses
Backbone.js Models, Collections, and Views in its Notifications system.
Backbone.js was selected because it was easy to fit into the structure
of the application, not the other way around. Automattic (the company
behind WordPress.com) is integrating Backbone.js into the Stats tab and
other features throughout the homepage.

Foursquare

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 homepage map and lists.

Bitbucket

Bitbucket is a free source code hosting service for Git and Mercurial.
Through its models and collections, Backbone.js has proved valuable in
supporting Bitbucket's REST API, as well as newer components such as
in-line code comments and approvals for pull requests. Mustache
templates provide server and client-side rendering, while a custom
Google Closure inspired life-cycle for widgets allows Bitbucket to
decorate existing DOM trees and insert new ones.

Disqus

Disqus chose Backbone.js to power the latest version of their commenting
widget. Backbone’s small footprint and easy extensibility made it the
right choice for Disqus’ 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.

Delicious

Delicious is a social bookmarking platform making it easy to save, sort,
and store bookmarks from across the web. Delicious uses Chaplin.js,
Backbone.js and AppCache to build a full-featured MVC web app. The use
of Backbone helped the website and mobile apps share a single API
service, and the reuse of the model tier made it significantly easier to
share code during the recent Delicious redesign.

Khan Academy

Khan Academy 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, jQuery and Handlebars, and most new
feature work is being pushed to the client side, greatly increasing the
quality of the API.

IRCCloud

IRCCloud is an always-connected IRC client that you use in your browser
— often leaving it open all day in a tab. The sleek web interface
communicates with an Erlang backend via websockets and the IRCCloud API.
It makes heavy use of Backbone.js events, models, views and routing to
keep your IRC conversations flowing in real time.

Pitchfork

Pitchfork uses Backbone.js to power its site-wide audio player,
Pitchfork.tv, location routing, a write-thru page fragment cache, and
more. Backbone.js (and Underscore.js) helps the team create clean and
modular components, move very quickly, and focus on the site, not the
spaghetti.

Spin

Spin pulls in the latest news stories from their internal API onto their
site using Backbone models and collections, and a custom sync 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.

ZocDoc

ZocDoc helps patients find local, in-network doctors and dentists, see
their real-time availability, and instantly book appointments. On the
public side, the webapp uses Backbone.js to handle client-side state and
rendering in search pages and doctor profiles. In addition, the new
version of the doctor-facing part of the website is a large single-page
application that benefits from Backbone's structure and modularity.
ZocDoc's Backbone classes are tested with Jasmine, and delivered to the
end user with Cassette.

Walmart Mobile

Walmart used Backbone.js to create the new version of their mobile web
application and created two new frameworks in the process. Thorax
provides mixins, inheritable events, as well as model and collection
view bindings that integrate directly with Handlebars templates. Lumbar
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.

Groupon Now!

Groupon Now! 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 — 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.

Basecamp

37Signals chose Backbone.js to create the calendar feature of its
popular project management software Basecamp. The Basecamp Calendar uses
Backbone.js models and views in conjunction with the Eco templating
system to present a polished, highly interactive group scheduling
interface.

Slavery Footprint

Slavery Footprint 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.

Stripe

Stripe provides an API for accepting credit cards on the web. Stripe's
management interface was recently rewritten from scratch in CoffeeScript
using Backbone.js as the primary framework, Eco for templates, Sass for
stylesheets, and Stitch to package everything together as CommonJS
modules. The new app uses Stripe's API directly for the majority of its
actions; Backbone.js models made it simple to map client-side models to
their corresponding RESTful resources.

Airbnb

Airbnb uses Backbone in many of its products. It started with Airbnb
Mobile Web (built in six weeks by a team of three) and has since grown
to Wish Lists, Match, Search, Communities, Payments, and Internal Tools.

SoundCloud Mobile

SoundCloud is the leading sound sharing platform on the internet, and
Backbone.js provides the foundation for SoundCloud Mobile. The project
uses the public SoundCloud API as a data source (channeled through a
nginx proxy), jQuery templates for the rendering, Qunit and PhantomJS
for the testing suite. The JS code, templates and CSS are built for the
production deployment with various Node.js tools like ready.js, Jake,
jsdom. The Backbone.History was modified to support the HTML5
history.pushState. Backbone.sync was extended with an additional
SessionStorage based cache layer.

Art.sy

Art.sy is a place to discover art you'll love. Art.sy is built on Rails,
using Grape to serve a robust JSON API. 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.

Pandora

When Pandora 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.

Inkling

Inkling is a cross-platform way to publish interactive learning content.
Inkling for Web uses Backbone.js to make hundreds of complex books —
from student textbooks to travel guides and programming manuals —
engaging and accessible on the web. Inkling supports WebGL-enabled 3D
graphics, interactive assessments, social sharing, and a system for
running practice code right in the book, 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. Give it a try with this excerpt
from JavaScript: The Definitive Guide.

Code School

Code School courses teach people about various programming topics like
CoffeeScript, CSS, Ruby on Rails, and more. The new Code School course
challenge page 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 jQuery DOM manipulation
and manual Ajax calls. Backbone.js helped introduce a new way to think
about developing an organized front-end application in JavaScript.

CloudApp

CloudApp is simple file and link sharing for the Mac. Backbone.js powers
the web tools which consume the documented API to manage Drops. Data is
either pulled manually or pushed by Pusher and fed to Mustache templates
for rendering. Check out the annotated source code to see the magic.

SeatGeek

SeatGeek's stadium ticket maps were originally developed with
Prototype.js. Moving to Backbone.js and jQuery 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.

Easel

Easel 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 rich visual editor
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.

Jolicloud

Jolicloud is an open and independent platform and operating system that
provides music playback, video streaming, photo browsing and document
editing — transforming low cost computers into beautiful cloud devices.
The new Jolicloud HTML5 app was built from the ground up using Backbone
and talks to the Jolicloud Platform, which is based on Node.js.
Jolicloud works offline using the HTML5 AppCache, extends Backbone.sync
to store data in IndexedDB or localStorage, and communicates with the
Joli OS via WebSockets.

Salon.io

Salon.io provides a space where photographers, artists and designers
freely arrange their visual art on virtual walls. Salon.io runs on
Rails, but does not use much of the traditional stack, as the entire
frontend is designed as a single page web app, using Backbone.js, Brunch
and CoffeeScript.

TileMill

Our fellow Knight Foundation News Challenge winners, MapBox, created an
open-source map design studio with Backbone.js: TileMill. TileMill lets
you manage map layers based on shapefiles and rasters, and edit their
appearance directly in the browser with the Carto styling language. Note
that the gorgeous MapBox homepage is also a Backbone.js app.

Blossom

Blossom is a lightweight project management tool for lean teams.
Backbone.js is heavily used in combination with CoffeeScript to provide
a smooth interaction experience. The app is packaged with Brunch. The
RESTful backend is built with Flask on Google App Engine.

Trello

Trello 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.

Tzigla

Cristi Balan and Irina Dumitrascu created Tzigla, a collaborative
drawing application where artists make tiles that connect to each other
to create surreal drawings. Backbone models help organize the code,
routers provide bookmarkable deep links, and the views are rendered with
haml.js and Zepto. Tzigla is written in Ruby (Rails) on the backend, and
CoffeeScript on the frontend, with Jammit prepackaging the static
assets.

Change Log

1.4.1 — Feb. 26, 2022 — Diff — Docs

-   Improved support for polymorphic collections in which two or more
    model types might have different idAttributes. Collection.modelId()
    overrides can now exploit the fact that internal methods pass the
    idAttribute as a second argument to modelId.
-   Fixed a temporary inconsistency in a collection's internal
    administration during model change events. Models (and by extension,
    collections) now emit a specialized changeId event when the id
    changes.
-   Fixed an issue where an ES6 class or object method could not be used
    as the model for a collection due to the lack of a prototype.
-   Restored continuous integration using GitHub Actions and
    cross-browser testing using Sauce Labs.
-   Several improvements to the online documentation.
-   Due to upgraded development tools, the annotated sources of the
    example code as well as the sourcemap of the minified bundle have
    changed filenames. Aliases and redirects in the old locations are
    kept for backwards compatibility.

1.4.0 — Feb. 19, 2019 — Diff — Docs

-   Collections now support the Javascript Iterator Protocol!
-   listenTo uses the listened object's public on method. This helps
    maintain interoperability between Backbone and other event libraries
    (including Node.js).
-   Added support for setting instance properties before the constructor
    in ES2015 classes with a preinitialize method.
-   Collection.get now checks if obj is a Model to allow retrieving
    models with an `attributes` key.
-   Fixed several issues with Router's URL hashing and parsing.

1.3.3 — Apr. 5, 2016 — Diff — Docs

-   Added findIndex and findLastIndex Underscore methods to Collection.
-   Added options.changes to Collection "update" event which includes
    added, merged, and removed models.
-   Added support for Collection#mixin and Model#mixin.
-   Ensured Collection#reduce and Collection#reduceRight work without an
    initial accumulator value.
-   Ensured Collection#_removeModels always returns an array.
-   Fixed a bug where Events.once with object syntax failed to bind
    context.
-   Fixed Collection#_onModelEvent regression where triggering a change
    event without a model would error.
-   Fixed Collection#set regression when parse returns a falsy value.
-   Fixed Model#id regression where id would be unintentionally
    undefined.
-   Fixed _removeModels regression which could cause an infinite loop
    under certain conditions.
-   Removed component package support.
-   Note that 1.3.3 fixes several bugs in versions 1.3.0 to 1.3.2.
    Please upgrade immediately if you are on one of those versions.

1.2.3 — Sept. 3, 2015 — Diff — Docs

-   Fixed a minor regression in 1.2.2 that would cause an error when
    adding a model to a collection at an out of bounds index.

1.2.2 — Aug. 19, 2015 — Diff — Docs

-   Collection methods find, filter, reject, every, some, and partition
    can now take a model-attributes-style predicate:
    this.collection.reject({user: 'guybrush'}).
-   Backbone Events once again supports multiple-event maps
    (obj.on({'error change': action})). This was a previously
    undocumented feature inadvertently removed in 1.2.0.
-   Added Collection#includes as an alias of Collection#contains and as
    a replacement for Collection#include in Underscore.js >= 1.8.

1.2.1 — Jun. 4, 2015 — Diff — Docs

-   Collection#add now avoids trying to parse a model instance when
    passed parse: false.
-   Bug fix in Collection#remove. The removed models are now actually
    returned.
-   Model#fetch no longer parses the response when passing parse: false.
-   Bug fix for iframe-based History when used with JSDOM.
-   Bug fix where Collection#invoke was not taking additional arguments.
-   When using on with an event map, you can now pass the context as the
    second argument. This was a previously undocumented feature
    inadvertently removed in 1.2.0.

1.2.0 — May 13, 2015 — Diff — Docs

-   Added new hooks to Views to allow them to work without jQuery. See
    the wiki page for more info.
-   As a neat side effect, Backbone.History no longer uses jQuery's
    event methods for pushState and hashChange listeners. We're native
    all the way.
-   Also on the subject of jQuery, if you're using Backbone with
    CommonJS (node, browserify, webpack) Backbone will automatically try
    to load jQuery for you.
-   Views now always delegate their events in setElement. You can no
    longer modify the events hash or your view's el property in
    initialize.
-   Added an "update" event that triggers after any amount of models are
    added or removed from a collection. Handy to re-render lists of
    things without debouncing.
-   Collection#at can take a negative index.
-   Added modelId to Collection for generating unique ids on polymorphic
    collections. Handy for cases when your model ids would otherwise
    collide.
-   Added an overridable _isModel for more advanced control of what's
    considered a model by your Collection.
-   The success callback passed to Model#destroy is always called
    asynchronously now.
-   Router#execute passes back the route name as its third argument.
-   Cancel the current Router transition by returning false in
    Router#execute. Great for checking logged-in status or other
    prerequisites.
-   Added getSearch and getPath methods to Backbone.History as
    cross-browser and overridable ways of slicing up the URL.
-   Added delegate and undelegate as finer-grained versions of
    delegateEvents and undelegateEvents. Useful for plugin authors to
    use a consistent events interface in Backbone.
-   A collection will only fire a "sort" event if its order was actually
    updated, not on every set.
-   Any passed options.attrs are now respected when saving a model with
    patch: true.
-   Collection#clone now sets the model and comparator functions of the
    cloned collection to the new one.
-   Adding models to your Collection when specifying an at position now
    sends the actual position of your model in the add event, not just
    the one you've passed in.
-   Collection#remove will now only return a list of models that have
    actually been removed from the collection.
-   Fixed loading Backbone.js in strict ES2015 module loaders.

1.1.2 — Feb. 20, 2014 — Diff — Docs

-   Backbone no longer tries to require jQuery in Node/CommonJS
    environments, for better compatibility with folks using Browserify.
    If you'd like to have Backbone use jQuery from Node, assign it like
    so: Backbone.$ = require('jquery');
-   Bugfix for route parameters with newlines in them.

1.1.1 — Feb. 13, 2014 — Diff — Docs

-   Backbone now registers itself for AMD (Require.js), Bower and
    Component, as well as being a CommonJS module and a regular
    (Java)Script. Whew.
-   Added an execute hook to the Router, which allows you to hook in and
    custom-parse route arguments, like query strings, for example.
-   Performance fine-tuning for Backbone Events.
-   Better matching for Unicode in routes, in old browsers.
-   Backbone Routers now handle query params in route fragments, passing
    them into the handler as the last argument. Routes specified as
    strings should no longer include the query string ('foo?:query'
    should be 'foo').

1.1.0 — Oct. 10, 2013 — Diff — Docs

-   Made the return values of Collection's set, add, remove, and reset
    more useful. Instead of returning this, they now return the changed
    (added, removed or updated) model or list of models.
-   Backbone Views no longer automatically attach options passed to the
    constructor as this.options and Backbone Models no longer attach url
    and urlRoot options, but you can do it yourself if you prefer.
-   All "invalid" events now pass consistent arguments. First the model
    in question, then the error object, then options.
-   You are no longer permitted to change the id of your model during
    parse. Use idAttribute instead.
-   On the other hand, parse is now an excellent place to extract and
    vivify incoming nested JSON into associated submodels.
-   Many tweaks, optimizations and bugfixes relating to Backbone 1.0,
    including URL overrides, mutation of options, bulk ordering,
    trailing slashes, edge-case listener leaks, nested model parsing...

1.0.0 — March 20, 2013 — Diff — Docs

-   Renamed Collection's "update" to set, for parallelism with the
    similar model.set(), and contrast with reset. It's now the default
    updating mechanism after a fetch. If you'd like to continue using
    "reset", pass {reset: true}.
-   Your route handlers will now receive their URL parameters
    pre-decoded.
-   Added listenToOnce as the analogue of once.
-   Added the findWhere method to Collections, similar to where.
-   Added the keys, values, pairs, invert, pick, and omit Underscore.js
    methods to Backbone Models.
-   The routes in a Router's route map may now be function literals,
    instead of references to methods, if you like.
-   url and urlRoot properties may now be passed as options when
    instantiating a new Model.

0.9.10 — Jan. 15, 2013 — Diff — Docs

-   A "route" event is triggered on the router in addition to being
    fired on Backbone.history.
-   Model validation is now only enforced by default in Model#save and
    no longer enforced by default upon construction or in Model#set,
    unless the {validate:true} option is passed.
-   View#make has been removed. You'll need to use $ directly to
    construct DOM elements now.
-   Passing {silent:true} on change will no longer delay individual
    "change:attr" events, instead they are silenced entirely.
-   The Model#change method has been removed, as delayed attribute
    changes are no longer available.
-   Bug fix on change where attribute comparison uses !== instead of
    _.isEqual.
-   Bug fix where an empty response from the server on save would not
    call the success function.
-   parse now receives options as its second argument.
-   Model validation now fires invalid event instead of error.

0.9.9 — Dec. 13, 2012 — Diff — Docs

-   Added listenTo and stopListening to Events. They can be used as
    inversion-of-control flavors of on and off, for convenient unbinding
    of all events an object is currently listening to. view.remove()
    automatically calls view.stopListening().
-   When using add on a collection, passing {merge: true} will now cause
    duplicate models to have their attributes merged in to the existing
    models, instead of being ignored.
-   Added update (which is also available as an option to fetch) for
    "smart" updating of sets of models.
-   HTTP PATCH support in save by passing {patch: true}.
-   The Backbone object now extends Events so that you can use it as a
    global event bus, if you like.
-   Added a "request" event to Backbone.sync, which triggers whenever a
    request begins to be made to the server. The natural complement to
    the "sync" event.
-   Router URLs now support optional parts via parentheses, without
    having to use a regex.
-   Backbone events now supports once, similar to Node's once, or
    jQuery's one.
-   Backbone events now support jQuery-style event maps
    obj.on({click: action}).
-   While listening to a reset event, the list of previous models is now
    available in options.previousModels, for convenience.
-   Validation now occurs even during "silent" changes. This change
    means that the isValid method has been removed. Failed validations
    also trigger an error, even if an error callback is specified in the
    options.
-   Consolidated "sync" and "error" events within Backbone.sync. They
    are now triggered regardless of the existence of success or error
    callbacks.
-   For mixed-mode APIs, Backbone.sync now accepts emulateHTTP and
    emulateJSON as inline options.
-   Collections now also proxy Underscore method name aliases (collect,
    inject, foldl, foldr, head, tail, take, and so on...)
-   Removed getByCid from Collections. collection.get now supports
    lookup by both id and cid.
-   After fetching a model or a collection, all defined parse functions
    will now be run. So fetching a collection and getting back new
    models could cause both the collection to parse the list, and then
    each model to be parsed in turn, if you have both functions defined.
-   Bugfix for normalizing leading and trailing slashes in the Router
    definitions. Their presence (or absence) should not affect behavior.
-   When declaring a View, options, el, tagName, id and className may
    now be defined as functions, if you want their values to be
    determined at runtime.
-   Added a Backbone.ajax hook for more convenient overriding of the
    default use of $.ajax. If AJAX is too passé, set it to your
    preferred method for server communication.
-   Collection#sort now triggers a sort event, instead of a reset event.
-   Calling destroy on a Model will now return false if the model isNew.
-   To set what library Backbone uses for DOM manipulation and Ajax
    calls, use Backbone.$ = ... instead of setDomLibrary.
-   Removed the Backbone.wrapError helper method. Overriding sync should
    work better for those particular use cases.
-   To improve the performance of add, options.index will no longer be
    set in the add event callback. collection.indexOf(model) can be used
    to retrieve the index of a model as necessary.
-   For semantic and cross browser reasons, routes will now ignore
    search parameters. Routes like search?query=…&page=3 should become
    search/…/3.
-   Model#set no longer accepts another model as an argument. This leads
    to subtle problems and is easily replaced with
    model.set(other.attributes).

0.9.2 — March 21, 2012 — Diff — Docs

-   Instead of throwing an error when adding duplicate models to a
    collection, Backbone will now silently skip them instead.
-   Added push, pop, unshift, and shift to collections.
-   A model's changed hash is now exposed for easy reading of the
    changed attribute delta, since the model's last "change" event.
-   Added where to collections for simple filtering.
-   You can now use a single off call to remove all callbacks bound to a
    specific object.
-   Bug fixes for nested individual change events, some of which may be
    "silent".
-   Bug fixes for URL encoding in location.hash fragments.
-   Bug fix for client-side validation in advance of a save call with
    {wait: true}.
-   Updated / refreshed the example Todo List app.

0.9.1 — Feb. 2, 2012 — Diff — Docs

-   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 isValid function that you can use to check if a
    model is currently in a valid state.
-   If you have multiple versions of jQuery on the page, you can now
    tell Backbone which one to use with Backbone.setDomLibrary.
-   Fixes regressions in 0.9.0 for routing with "root", saving with both
    "wait" and "validate", and the order of nested "change" events.

0.9.0 — Jan. 30, 2012 — Diff — Docs

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

0.5.3 — August 9, 2011 — Diff — Docs
A View's events property may now be defined as a function, as well as an
object literal, making it easier to programmatically define and inherit
events. groupBy is now proxied from Underscore as a method on
Collections. If the server has already rendered everything on page load,
pass Backbone.history.start({silent: true}) to prevent the initial route
from triggering. Bugfix for pushState with encoded URLs.

0.5.2 — July 26, 2011 — Diff — Docs
The bind function, can now take an optional third argument, to specify
the this of the callback function. Multiple models with the same id are
now allowed in a collection. Fixed a bug where calling
.fetch(jQueryOptions) could cause an incorrect URL to be serialized.
Fixed a brief extra route fire before redirect, when degrading from
pushState.

0.5.1 — July 5, 2011 — Diff — Docs
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 Model#initialize. Reverted
a 0.5.0 change that would strip leading hashbangs from routes. Added
contains as an alias for includes.

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

0.3.3 — Dec 1, 2010 — Diff — Docs
Backbone.js now supports Zepto, alongside jQuery, as a framework for DOM
manipulation and Ajax support. Implemented Model#escape, to efficiently
handle attributes intended for HTML interpolation. When trying to
persist a model, failed requests will now trigger an "error" event. The
ubiquitous options argument is now passed as the final argument to all
"change" events.

0.3.2 — Nov 23, 2010 — Diff — Docs
Bugfix for IE7 + iframe-based "hashchange" events. sync may now be
overridden on a per-model, or per-collection basis. Fixed recursion
error when calling save with no changed attributes, within a "change"
event.

0.3.1 — Nov 15, 2010 — Diff — Docs
All "add" and "remove" events are now sent through the model, so that
views can listen for them without having to know about the collection.
Added a remove method to Backbone.View. toJSON is no longer called at
all for 'read' and 'delete' requests. Backbone routes are now able to
load empty URL fragments.

0.3.0 — Nov 9, 2010 — Diff — Docs
Backbone now has Controllers and History, for doing client-side routing
based on URL fragments. Added emulateHTTP to provide support for legacy
servers that don't do PUT and DELETE. Added emulateJSON for servers that
can't accept application/json encoded requests. Added Model#clear, which
removes all attributes from a model. All Backbone classes may now be
seamlessly inherited by CoffeeScript classes.

0.2.0 — Oct 25, 2010 — Diff — Docs
Instead of requiring server responses to be namespaced under a model
key, now you can define your own parse method to convert responses into
attributes for Models and Collections. The old handleEvents function is
now named delegateEvents, and is automatically called as part of the
View's constructor. Added a toJSON function to Collections. Added
Underscore's chain to Collections.

0.1.2 — Oct 19, 2010 — Diff — Docs
Added a Model#fetch method for refreshing the attributes of single model
from the server. An error callback may now be passed to set and save as
an option, which will be invoked if validation fails, overriding the
"error" event. You can now tell backbone to use the _method hack instead
of HTTP methods by setting Backbone.emulateHTTP = true. Existing Model
and Collection data is no longer sent up unnecessarily with GET and
DELETE requests. Added a rake lint task. Backbone is now published as an
NPM module.

0.1.1 — Oct 14, 2010 — Diff — Docs
Added a convention for initialize functions to be called upon instance
construction, if defined. Documentation tweaks.

0.1.0 — Oct 13, 2010 — Docs
Initial Backbone release.

A DocumentCloud Project
