# backbone.js

¶

    Backbone.js 0.9.2

¶

    (c) 2010-2012 Jeremy Ashkenas, DocumentCloud Inc.
    Backbone may be freely distributed under the MIT license.
    For all details and documentation:
    http://backbonejs.org

    (function(){

¶

## Initial Setup

¶

Save a reference to the global object (`window` in the browser, `global` on the server).

      var root = this;

¶

Save the previous value of the `Backbone` variable, so that it can be restored later on, if `noConflict` is used.

      var previousBackbone = root.Backbone;

¶

Create a local reference to slice/splice.

      var slice = Array.prototype.slice;
      var splice = Array.prototype.splice;

¶

The top-level namespace. All public Backbone classes and modules will be attached to this. Exported for both CommonJS and the browser.

      var Backbone;
      if (typeof exports !== 'undefined') {
        Backbone = exports;
      } else {
        Backbone = root.Backbone = {};
      }

¶

Current version of the library. Keep in sync with `package.json`.

      Backbone.VERSION = '0.9.2';

¶

Require Underscore, if we're on the server, and it's not already present.

      var _ = root._;
      if (!_ && (typeof require !== 'undefined')) _ = require('underscore');

¶

For Backbone's purposes, jQuery, Zepto, or Ender owns the `$` variable.

      var $ = root.jQuery || root.Zepto || root.ender;

¶

Set the JavaScript library that will be used for DOM manipulation and Ajax calls (a.k.a. the `$` variable). By default Backbone will use: jQuery, Zepto, or Ender; but the `setDomLibrary()` method lets you inject an alternate JavaScript library (or a mock library for testing your views outside of a browser).

      Backbone.setDomLibrary = function(lib) {
        $ = lib;
      };

¶

Runs Backbone.js in noConflict mode, returning the `Backbone` variable to its previous owner. Returns a reference to this Backbone object.

      Backbone.noConflict = function() {
        root.Backbone = previousBackbone;
        return this;
      };

¶

Turn on `emulateHTTP` to support legacy HTTP servers. Setting this option will fake `"PUT"` and `"DELETE"` requests via the `_method` parameter and set a `X-Http-Method-Override` header.

      Backbone.emulateHTTP = false;

¶

Turn on `emulateJSON` to support legacy servers that can't deal with direct `application/json` requests ... will encode the body as `application/x-www-form-urlencoded` instead and will send the model in a form param named `model`.

      Backbone.emulateJSON = false;

¶

## Backbone.Events

¶

Regular expression used to split event strings

      var eventSplitter = /\s+/;

¶

A module that can be mixed in to any object in order to provide it with custom events. You may bind with `on` or remove with `off` callback functions to an event; trigger`-ing an event fires all callbacks in succession.

    var object = {};
    _.extend(object, Backbone.Events);
    object.on('expand', function(){ alert('expanded'); });
    object.trigger('expand');

      var Events = Backbone.Events = {

¶

Bind one or more space separated events, `events`, to a `callback` function. Passing `"all"` will bind the callback to all events fired.

        on: function(events, callback, context) {

          var calls, event, node, tail, list;
          if (!callback) return this;
          events = events.split(eventSplitter);
          calls = this._callbacks || (this._callbacks = {});

¶

Create an immutable callback list, allowing traversal during modification. The tail is an empty object that will always be used as the next node.

          while (event = events.shift()) {
            list = calls[event];
            node = list ? list.tail : {};
            node.next = tail = {};
            node.context = context;
            node.callback = callback;
            calls[event] = {tail: tail, next: list ? list.next : node};
          }

          return this;
        },

¶

Remove one or many callbacks. If `context` is null, removes all callbacks with that function. If `callback` is null, removes all callbacks for the event. If `events` is null, removes all bound callbacks for all events.

        off: function(events, callback, context) {
          var event, calls, node, tail, cb, ctx;

¶

No events, or removing all events.

          if (!(calls = this._callbacks)) return;
          if (!(events || callback || context)) {
            delete this._callbacks;
            return this;
          }

¶

Loop through the listed events and contexts, splicing them out of the linked list of callbacks if appropriate.

          events = events ? events.split(eventSplitter) : _.keys(calls);
          while (event = events.shift()) {
            node = calls[event];
            delete calls[event];
            if (!node || !(callback || context)) continue;

¶

Create a new list, omitting the indicated callbacks.

            tail = node.tail;
            while ((node = node.next) !== tail) {
              cb = node.callback;
              ctx = node.context;
              if ((callback && cb !== callback) || (context && ctx !== context)) {
                this.on(event, cb, ctx);
              }
            }
          }

          return this;
        },

¶

Trigger one or many events, firing all bound callbacks. Callbacks are passed the same arguments as `trigger` is, apart from the event name (unless you're listening on `"all"`, which will cause your callback to receive the true name of the event as the first argument).

        trigger: function(events) {
          var event, node, calls, tail, args, all, rest;
          if (!(calls = this._callbacks)) return this;
          all = calls.all;
          events = events.split(eventSplitter);
          rest = slice.call(arguments, 1);

¶

For each event, walk through the linked list of callbacks twice, first to trigger the event, then to trigger any `"all"` callbacks.

          while (event = events.shift()) {
            if (node = calls[event]) {
              tail = node.tail;
              while ((node = node.next) !== tail) {
                node.callback.apply(node.context || this, rest);
              }
            }
            if (node = all) {
              tail = node.tail;
              args = [event].concat(rest);
              while ((node = node.next) !== tail) {
                node.callback.apply(node.context || this, args);
              }
            }
          }

          return this;
        }

      };

¶

Aliases for backwards compatibility.

      Events.bind   = Events.on;
      Events.unbind = Events.off;

¶

## Backbone.Model

¶

Create a new model, with defined attributes. A client id (`cid`) is automatically generated and assigned for you.

      var Model = Backbone.Model = function(attributes, options) {
        var defaults;
        attributes || (attributes = {});
        if (options && options.parse) attributes = this.parse(attributes);
        if (defaults = getValue(this, 'defaults')) {
          attributes = _.extend({}, defaults, attributes);
        }
        if (options && options.collection) this.collection = options.collection;
        this.attributes = {};
        this._escapedAttributes = {};
        this.cid = _.uniqueId('c');
        this.changed = {};
        this._silent = {};
        this._pending = {};
        this.set(attributes, {silent: true});

¶

Reset change tracking.

        this.changed = {};
        this._silent = {};
        this._pending = {};
        this._previousAttributes = _.clone(this.attributes);
        this.initialize.apply(this, arguments);
      };

¶

Attach all inheritable methods to the Model prototype.

      _.extend(Model.prototype, Events, {

¶

A hash of attributes whose current and previous value differ.

        changed: null,

¶

A hash of attributes that have silently changed since the last time `change` was called. Will become pending attributes on the next call.

        _silent: null,

¶

A hash of attributes that have changed since the last `'change'` event began.

        _pending: null,

¶

The default name for the JSON `id` attribute is `"id"`. MongoDB and CouchDB users may want to set this to `"_id"`.

        idAttribute: 'id',

¶

Initialize is an empty function by default. Override it with your own initialization logic.

        initialize: function(){},

¶

Return a copy of the model's `attributes` object.

        toJSON: function(options) {
          return _.clone(this.attributes);
        },

¶

Get the value of an attribute.

        get: function(attr) {
          return this.attributes[attr];
        },

¶

Get the HTML-escaped value of an attribute.

        escape: function(attr) {
          var html;
          if (html = this._escapedAttributes[attr]) return html;
          var val = this.get(attr);
          return this._escapedAttributes[attr] = _.escape(val == null ? '' : '' + val);
        },

¶

Returns `true` if the attribute contains a value that is not null or undefined.

        has: function(attr) {
          return this.get(attr) != null;
        },

¶

Set a hash of model attributes on the object, firing `"change"` unless you choose to silence it.

        set: function(key, value, options) {
          var attrs, attr, val;

¶

Handle both

          if (_.isObject(key) || key == null) {
            attrs = key;
            options = value;
          } else {
            attrs = {};
            attrs[key] = value;
          }

¶

Extract attributes and options.

          options || (options = {});
          if (!attrs) return this;
          if (attrs instanceof Model) attrs = attrs.attributes;
          if (options.unset) for (attr in attrs) attrs[attr] = void 0;

¶

Run validation.

          if (!this._validate(attrs, options)) return false;

¶

Check for changes of `id`.

          if (this.idAttribute in attrs) this.id = attrs[this.idAttribute];

          var changes = options.changes = {};
          var now = this.attributes;
          var escaped = this._escapedAttributes;
          var prev = this._previousAttributes || {};

¶

For each `set` attribute...

          for (attr in attrs) {
            val = attrs[attr];

¶

If the new and current value differ, record the change.

            if (!_.isEqual(now[attr], val) || (options.unset && _.has(now, attr))) {
              delete escaped[attr];
              (options.silent ? this._silent : changes)[attr] = true;
            }

¶

Update or delete the current value.

            options.unset ? delete now[attr] : now[attr] = val;

¶

If the new and previous value differ, record the change. If not, then remove changes for this attribute.

            if (!_.isEqual(prev[attr], val) || (_.has(now, attr) != _.has(prev, attr))) {
              this.changed[attr] = val;
              if (!options.silent) this._pending[attr] = true;
            } else {
              delete this.changed[attr];
              delete this._pending[attr];
            }
          }

¶

Fire the `"change"` events.

          if (!options.silent) this.change(options);
          return this;
        },

¶

Remove an attribute from the model, firing `"change"` unless you choose to silence it. `unset` is a noop if the attribute doesn't exist.

        unset: function(attr, options) {
          (options || (options = {})).unset = true;
          return this.set(attr, null, options);
        },

¶

Clear all attributes on the model, firing `"change"` unless you choose to silence it.

        clear: function(options) {
          (options || (options = {})).unset = true;
          return this.set(_.clone(this.attributes), options);
        },

¶

Fetch the model from the server. If the server's representation of the model differs from its current attributes, they will be overriden, triggering a `"change"` event.

        fetch: function(options) {
          options = options ? _.clone(options) : {};
          var model = this;
          var success = options.success;
          options.success = function(resp, status, xhr) {
            if (!model.set(model.parse(resp, xhr), options)) return false;
            if (success) success(model, resp);
          };
          options.error = Backbone.wrapError(options.error, model, options);
          return (this.sync || Backbone.sync).call(this, 'read', this, options);
        },

¶

Set a hash of model attributes, and sync the model to the server. If the server returns an attributes hash that differs, the model's state will be `set` again.

        save: function(key, value, options) {
          var attrs, current;

¶

Handle both `("key", value)` and `({key: value})` -style calls.

          if (_.isObject(key) || key == null) {
            attrs = key;
            options = value;
          } else {
            attrs = {};
            attrs[key] = value;
          }
          options = options ? _.clone(options) : {};

¶

If we're "wait"-ing to set changed attributes, validate early.

          if (options.wait) {
            if (!this._validate(attrs, options)) return false;
            current = _.clone(this.attributes);
          }

¶

Regular saves `set` attributes before persisting to the server.

          var silentOptions = _.extend({}, options, {silent: true});
          if (attrs && !this.set(attrs, options.wait ? silentOptions : options)) {
            return false;
          }

¶

After a successful server-side save, the client is (optionally) updated with the server-side state.

          var model = this;
          var success = options.success;
          options.success = function(resp, status, xhr) {
            var serverAttrs = model.parse(resp, xhr);
            if (options.wait) {
              delete options.wait;
              serverAttrs = _.extend(attrs || {}, serverAttrs);
            }
            if (!model.set(serverAttrs, options)) return false;
            if (success) {
              success(model, resp);
            } else {
              model.trigger('sync', model, resp, options);
            }
          };

¶

Finish configuring and sending the Ajax request.

          options.error = Backbone.wrapError(options.error, model, options);
          var method = this.isNew() ? 'create' : 'update';
          var xhr = (this.sync || Backbone.sync).call(this, method, this, options);
          if (options.wait) this.set(current, silentOptions);
          return xhr;
        },

¶

Destroy this model on the server if it was already persisted. Optimistically removes the model from its collection, if it has one. If `wait: true` is passed, waits for the server to respond before removal.

        destroy: function(options) {
          options = options ? _.clone(options) : {};
          var model = this;
          var success = options.success;

          var triggerDestroy = function() {
            model.trigger('destroy', model, model.collection, options);
          };

          if (this.isNew()) {
            triggerDestroy();
            return false;
          }

          options.success = function(resp) {
            if (options.wait) triggerDestroy();
            if (success) {
              success(model, resp);
            } else {
              model.trigger('sync', model, resp, options);
            }
          };

          options.error = Backbone.wrapError(options.error, model, options);
          var xhr = (this.sync || Backbone.sync).call(this, 'delete', this, options);
          if (!options.wait) triggerDestroy();
          return xhr;
        },

¶

Default URL for the model's representation on the server -- if you're using Backbone's restful methods, override this to change the endpoint that will be called.

        url: function() {
          var base = getValue(this, 'urlRoot') || getValue(this.collection, 'url') || urlError();
          if (this.isNew()) return base;
          return base + (base.charAt(base.length - 1) == '/' ? '' : '/') + encodeURIComponent(this.id);
        },

¶

parse converts a response into the hash of attributes to be `set` on the model. The default implementation is just to pass the response along.

        parse: function(resp, xhr) {
          return resp;
        },

¶

Create a new model with identical attributes to this one.

        clone: function() {
          return new this.constructor(this.attributes);
        },

¶

A model is new if it has never been saved to the server, and lacks an id.

        isNew: function() {
          return this.id == null;
        },

¶

Call this method to manually fire a `"change"` event for this model and a `"change:attribute"` event for each changed attribute. Calling this will cause all objects observing the model to update.

        change: function(options) {
          options || (options = {});
          var changing = this._changing;
          this._changing = true;

¶

Silent changes become pending changes.

          for (var attr in this._silent) this._pending[attr] = true;

¶

Silent changes are triggered.

          var changes = _.extend({}, options.changes, this._silent);
          this._silent = {};
          for (var attr in changes) {
            this.trigger('change:' + attr, this, this.get(attr), options);
          }
          if (changing) return this;

¶

Continue firing `"change"` events while there are pending changes.

          while (!_.isEmpty(this._pending)) {
            this._pending = {};
            this.trigger('change', this, options);

¶

Pending and silent changes still remain.

            for (var attr in this.changed) {
              if (this._pending[attr] || this._silent[attr]) continue;
              delete this.changed[attr];
            }
            this._previousAttributes = _.clone(this.attributes);
          }

          this._changing = false;
          return this;
        },

¶

Determine if the model has changed since the last `"change"` event. If you specify an attribute name, determine if that attribute has changed.

        hasChanged: function(attr) {
          if (!arguments.length) return !_.isEmpty(this.changed);
          return _.has(this.changed, attr);
        },

¶

Return an object containing all the attributes that have changed, or false if there are no changed attributes. Useful for determining what parts of a view need to be updated and/or what attributes need to be persisted to the server. Unset attributes will be set to undefined. You can also pass an attributes object to diff against the model, determining if there would be a change.

        changedAttributes: function(diff) {
          if (!diff) return this.hasChanged() ? _.clone(this.changed) : false;
          var val, changed = false, old = this._previousAttributes;
          for (var attr in diff) {
            if (_.isEqual(old[attr], (val = diff[attr]))) continue;
            (changed || (changed = {}))[attr] = val;
          }
          return changed;
        },

¶

Get the previous value of an attribute, recorded at the time the last `"change"` event was fired.

        previous: function(attr) {
          if (!arguments.length || !this._previousAttributes) return null;
          return this._previousAttributes[attr];
        },

¶

Get all of the attributes of the model at the time of the previous `"change"` event.

        previousAttributes: function() {
          return _.clone(this._previousAttributes);
        },

¶

Check if the model is currently in a valid state. It's only possible to get into an invalid state if you're using silent changes.

        isValid: function() {
          return !this.validate(this.attributes);
        },

¶

Run validation against the next complete set of model attributes, returning `true` if all is well. If a specific `error` callback has been passed, call that instead of firing the general `"error"` event.

        _validate: function(attrs, options) {
          if (options.silent || !this.validate) return true;
          attrs = _.extend({}, this.attributes, attrs);
          var error = this.validate(attrs, options);
          if (!error) return true;
          if (options && options.error) {
            options.error(this, error, options);
          } else {
            this.trigger('error', this, error, options);
          }
          return false;
        }

      });

¶

## Backbone.Collection

¶

Provides a standard collection class for our sets of models, ordered or unordered. If a `comparator` is specified, the Collection will maintain its models in sort order, as they're added and removed.

      var Collection = Backbone.Collection = function(models, options) {
        options || (options = {});
        if (options.model) this.model = options.model;
        if (options.comparator) this.comparator = options.comparator;
        this._reset();
        this.initialize.apply(this, arguments);
        if (models) this.reset(models, {silent: true, parse: options.parse});
      };

¶

Define the Collection's inheritable methods.

      _.extend(Collection.prototype, Events, {

¶

The default model for a collection is just a Backbone.Model. This should be overridden in most cases.

        model: Model,

¶

Initialize is an empty function by default. Override it with your own initialization logic.

        initialize: function(){},

¶

The JSON representation of a Collection is an array of the models' attributes.

        toJSON: function(options) {
          return this.map(function(model){ return model.toJSON(options); });
        },

¶

Add a model, or list of models to the set. Pass silent to avoid firing the `add` event for every new model.

        add: function(models, options) {
          var i, index, length, model, cid, id, cids = {}, ids = {}, dups = [];
          options || (options = {});
          models = _.isArray(models) ? models.slice() : [models];

¶

Begin by turning bare objects into model references, and preventing invalid models or duplicate models from being added.

          for (i = 0, length = models.length; i < length; i++) {
            if (!(model = models[i] = this._prepareModel(models[i], options))) {
              throw new Error("Can't add an invalid model to a collection");
            }
            cid = model.cid;
            id = model.id;
            if (cids[cid] || this._byCid[cid] || ((id != null) && (ids[id] || this._byId[id]))) {
              dups.push(i);
              continue;
            }
            cids[cid] = ids[id] = model;
          }

¶

Remove duplicates.

          i = dups.length;
          while (i--) {
            models.splice(dups[i], 1);
          }

¶

Listen to added models' events, and index models for lookup by `id` and by `cid`.

          for (i = 0, length = models.length; i < length; i++) {
            (model = models[i]).on('all', this._onModelEvent, this);
            this._byCid[model.cid] = model;
            if (model.id != null) this._byId[model.id] = model;
          }

¶

Insert models into the collection, re-sorting if needed, and triggering `add` events unless silenced.

          this.length += length;
          index = options.at != null ? options.at : this.models.length;
          splice.apply(this.models, [index, 0].concat(models));
          if (this.comparator) this.sort({silent: true});
          if (options.silent) return this;
          for (i = 0, length = this.models.length; i < length; i++) {
            if (!cids[(model = this.models[i]).cid]) continue;
            options.index = i;
            model.trigger('add', model, this, options);
          }
          return this;
        },

¶

Remove a model, or a list of models from the set. Pass silent to avoid firing the `remove` event for every model removed.

        remove: function(models, options) {
          var i, l, index, model;
          options || (options = {});
          models = _.isArray(models) ? models.slice() : [models];
          for (i = 0, l = models.length; i < l; i++) {
            model = this.getByCid(models[i]) || this.get(models[i]);
            if (!model) continue;
            delete this._byId[model.id];
            delete this._byCid[model.cid];
            index = this.indexOf(model);
            this.models.splice(index, 1);
            this.length--;
            if (!options.silent) {
              options.index = index;
              model.trigger('remove', model, this, options);
            }
            this._removeReference(model);
          }
          return this;
        },

¶

Add a model to the end of the collection.

        push: function(model, options) {
          model = this._prepareModel(model, options);
          this.add(model, options);
          return model;
        },

¶

Remove a model from the end of the collection.

        pop: function(options) {
          var model = this.at(this.length - 1);
          this.remove(model, options);
          return model;
        },

¶

Add a model to the beginning of the collection.

        unshift: function(model, options) {
          model = this._prepareModel(model, options);
          this.add(model, _.extend({at: 0}, options));
          return model;
        },

¶

Remove a model from the beginning of the collection.

        shift: function(options) {
          var model = this.at(0);
          this.remove(model, options);
          return model;
        },

¶

Get a model from the set by id.

        get: function(id) {
          if (id == null) return void 0;
          return this._byId[id.id != null ? id.id : id];
        },

¶

Get a model from the set by client id.

        getByCid: function(cid) {
          return cid && this._byCid[cid.cid || cid];
        },

¶

Get the model at the given index.

        at: function(index) {
          return this.models[index];
        },

¶

Return models with matching attributes. Useful for simple cases of `filter`.

        where: function(attrs) {
          if (_.isEmpty(attrs)) return [];
          return this.filter(function(model) {
            for (var key in attrs) {
              if (attrs[key] !== model.get(key)) return false;
            }
            return true;
          });
        },

¶

Force the collection to re-sort itself. You don't need to call this under normal circumstances, as the set will maintain sort order as each item is added.

        sort: function(options) {
          options || (options = {});
          if (!this.comparator) throw new Error('Cannot sort a set without a comparator');
          var boundComparator = _.bind(this.comparator, this);
          if (this.comparator.length == 1) {
            this.models = this.sortBy(boundComparator);
          } else {
            this.models.sort(boundComparator);
          }
          if (!options.silent) this.trigger('reset', this, options);
          return this;
        },

¶

Pluck an attribute from each model in the collection.

        pluck: function(attr) {
          return _.map(this.models, function(model){ return model.get(attr); });
        },

¶

When you have more items than you want to add or remove individually, you can reset the entire set with a new list of models, without firing any `add` or `remove` events. Fires `reset` when finished.

        reset: function(models, options) {
          models  || (models = []);
          options || (options = {});
          for (var i = 0, l = this.models.length; i < l; i++) {
            this._removeReference(this.models[i]);
          }
          this._reset();
          this.add(models, _.extend({silent: true}, options));
          if (!options.silent) this.trigger('reset', this, options);
          return this;
        },

¶

Fetch the default set of models for this collection, resetting the collection when they arrive. If `add: true` is passed, appends the models to the collection instead of resetting.

        fetch: function(options) {
          options = options ? _.clone(options) : {};
          if (options.parse === undefined) options.parse = true;
          var collection = this;
          var success = options.success;
          options.success = function(resp, status, xhr) {
            collection[options.add ? 'add' : 'reset'](collection.parse(resp, xhr), options);
            if (success) success(collection, resp);
          };
          options.error = Backbone.wrapError(options.error, collection, options);
          return (this.sync || Backbone.sync).call(this, 'read', this, options);
        },

¶

Create a new instance of a model in this collection. Add the model to the collection immediately, unless `wait: true` is passed, in which case we wait for the server to agree.

        create: function(model, options) {
          var coll = this;
          options = options ? _.clone(options) : {};
          model = this._prepareModel(model, options);
          if (!model) return false;
          if (!options.wait) coll.add(model, options);
          var success = options.success;
          options.success = function(nextModel, resp, xhr) {
            if (options.wait) coll.add(nextModel, options);
            if (success) {
              success(nextModel, resp);
            } else {
              nextModel.trigger('sync', model, resp, options);
            }
          };
          model.save(null, options);
          return model;
        },

¶

parse converts a response into a list of models to be added to the collection. The default implementation is just to pass it through.

        parse: function(resp, xhr) {
          return resp;
        },

¶

Proxy to _'s chain. Can't be proxied the same way the rest of the underscore methods are proxied because it relies on the underscore constructor.

        chain: function () {
          return _(this.models).chain();
        },

¶

Reset all internal state. Called when the collection is reset.

        _reset: function(options) {
          this.length = 0;
          this.models = [];
          this._byId  = {};
          this._byCid = {};
        },

¶

Prepare a model or hash of attributes to be added to this collection.

        _prepareModel: function(model, options) {
          options || (options = {});
          if (!(model instanceof Model)) {
            var attrs = model;
            options.collection = this;
            model = new this.model(attrs, options);
            if (!model._validate(model.attributes, options)) model = false;
          } else if (!model.collection) {
            model.collection = this;
          }
          return model;
        },

¶

Internal method to remove a model's ties to a collection.

        _removeReference: function(model) {
          if (this == model.collection) {
            delete model.collection;
          }
          model.off('all', this._onModelEvent, this);
        },

¶

Internal method called every time a model in the set fires an event. Sets need to update their indexes when models change ids. All other events simply proxy through. "add" and "remove" events that originate in other collections are ignored.

        _onModelEvent: function(event, model, collection, options) {
          if ((event == 'add' || event == 'remove') && collection != this) return;
          if (event == 'destroy') {
            this.remove(model, options);
          }
          if (model && event === 'change:' + model.idAttribute) {
            delete this._byId[model.previous(model.idAttribute)];
            this._byId[model.id] = model;
          }
          this.trigger.apply(this, arguments);
        }

      });

¶

Underscore methods that we want to implement on the Collection.

      var methods = ['forEach', 'each', 'map', 'reduce', 'reduceRight', 'find',
        'detect', 'filter', 'select', 'reject', 'every', 'all', 'some', 'any',
        'include', 'contains', 'invoke', 'max', 'min', 'sortBy', 'sortedIndex',
        'toArray', 'size', 'first', 'initial', 'rest', 'last', 'without', 'indexOf',
        'shuffle', 'lastIndexOf', 'isEmpty', 'groupBy'];

¶

Mix in each Underscore method as a proxy to `Collection#models`.

      _.each(methods, function(method) {
        Collection.prototype[method] = function() {
          return _[method].apply(_, [this.models].concat(_.toArray(arguments)));
        };
      });

¶

## Backbone.Router

¶

Routers map faux-URLs to actions, and fire events when routes are matched. Creating a new one sets its `routes` hash, if not set statically.

      var Router = Backbone.Router = function(options) {
        options || (options = {});
        if (options.routes) this.routes = options.routes;
        this._bindRoutes();
        this.initialize.apply(this, arguments);
      };

¶

Cached regular expressions for matching named param parts and splatted parts of route strings.

      var namedParam    = /:\w+/g;
      var splatParam    = /\*\w+/g;
      var escapeRegExp  = /[-[\]{}()+?.,\\^$|#\s]/g;

¶

Set up all inheritable Backbone.Router properties and methods.

      _.extend(Router.prototype, Events, {

¶

Initialize is an empty function by default. Override it with your own initialization logic.

        initialize: function(){},

¶

Manually bind a single named route to a callback. For example:

    this.route('search/:query/p:num', 'search', function(query, num) {
      ...
    });

        route: function(route, name, callback) {
          Backbone.history || (Backbone.history = new History);
          if (!_.isRegExp(route)) route = this._routeToRegExp(route);
          if (!callback) callback = this[name];
          Backbone.history.route(route, _.bind(function(fragment) {
            var args = this._extractParameters(route, fragment);
            callback && callback.apply(this, args);
            this.trigger.apply(this, ['route:' + name].concat(args));
            Backbone.history.trigger('route', this, name, args);
          }, this));
          return this;
        },

¶

Simple proxy to `Backbone.history` to save a fragment into the history.

        navigate: function(fragment, options) {
          Backbone.history.navigate(fragment, options);
        },

¶

Bind all defined routes to `Backbone.history`. We have to reverse the order of the routes here to support behavior where the most general routes can be defined at the bottom of the route map.

        _bindRoutes: function() {
          if (!this.routes) return;
          var routes = [];
          for (var route in this.routes) {
            routes.unshift([route, this.routes[route]]);
          }
          for (var i = 0, l = routes.length; i < l; i++) {
            this.route(routes[i][0], routes[i][1], this[routes[i][1]]);
          }
        },

¶

Convert a route string into a regular expression, suitable for matching against the current location hash.

        _routeToRegExp: function(route) {
          route = route.replace(escapeRegExp, '\\$&')
                       .replace(namedParam, '([^\/]+)')
                       .replace(splatParam, '(.*?)');
          return new RegExp('^' + route + '$');
        },

¶

Given a route, and a URL fragment that it matches, return the array of extracted parameters.

        _extractParameters: function(route, fragment) {
          return route.exec(fragment).slice(1);
        }

      });

¶

## Backbone.History

¶

Handles cross-browser history management, based on URL fragments. If the browser does not support `onhashchange`, falls back to polling.

      var History = Backbone.History = function() {
        this.handlers = [];
        _.bindAll(this, 'checkUrl');
      };

¶

Cached regex for cleaning leading hashes and slashes .

      var routeStripper = /^[#\/]/;

¶

Cached regex for detecting MSIE.

      var isExplorer = /msie [\w.]+/;

¶

Has the history handling already been started?

      History.started = false;

¶

Set up all inheritable Backbone.History properties and methods.

      _.extend(History.prototype, Events, {

¶

The default interval to poll for hash changes, if necessary, is twenty times a second.

        interval: 50,

¶

Gets the true hash value. Cannot use location.hash directly due to bug in Firefox where location.hash will always be decoded.

        getHash: function(windowOverride) {
          var loc = windowOverride ? windowOverride.location : window.location;
          var match = loc.href.match(/#(.*)$/);
          return match ? match[1] : '';
        },

¶

Get the cross-browser normalized URL fragment, either from the URL, the hash, or the override.

        getFragment: function(fragment, forcePushState) {
          if (fragment == null) {
            if (this._hasPushState || forcePushState) {
              fragment = window.location.pathname;
              var search = window.location.search;
              if (search) fragment += search;
            } else {
              fragment = this.getHash();
            }
          }
          if (!fragment.indexOf(this.options.root)) fragment = fragment.substr(this.options.root.length);
          return fragment.replace(routeStripper, '');
        },

¶

Start the hash change handling, returning `true` if the current URL matches an existing route, and `false` otherwise.

        start: function(options) {
          if (History.started) throw new Error("Backbone.history has already been started");
          History.started = true;

¶

Figure out the initial configuration. Do we need an iframe? Is pushState desired ... is it available?

          this.options          = _.extend({}, {root: '/'}, this.options, options);
          this._wantsHashChange = this.options.hashChange !== false;
          this._wantsPushState  = !!this.options.pushState;
          this._hasPushState    = !!(this.options.pushState && window.history && window.history.pushState);
          var fragment          = this.getFragment();
          var docMode           = document.documentMode;
          var oldIE             = (isExplorer.exec(navigator.userAgent.toLowerCase()) && (!docMode || docMode <= 7));

          if (oldIE) {
            this.iframe = $('<iframe src="javascript:0" tabindex="-1" />').hide().appendTo('body')[0].contentWindow;
            this.navigate(fragment);
          }

¶

Depending on whether we're using pushState or hashes, and whether 'onhashchange' is supported, determine how we check the URL state.

          if (this._hasPushState) {
            $(window).bind('popstate', this.checkUrl);
          } else if (this._wantsHashChange && ('onhashchange' in window) && !oldIE) {
            $(window).bind('hashchange', this.checkUrl);
          } else if (this._wantsHashChange) {
            this._checkUrlInterval = setInterval(this.checkUrl, this.interval);
          }

¶

Determine if we need to change the base url, for a pushState link opened by a non-pushState browser.

          this.fragment = fragment;
          var loc = window.location;
          var atRoot  = loc.pathname == this.options.root;

¶

If we've started off with a route from a `pushState`-enabled browser, but we're currently in a browser that doesn't support it...

          if (this._wantsHashChange && this._wantsPushState && !this._hasPushState && !atRoot) {
            this.fragment = this.getFragment(null, true);
            window.location.replace(this.options.root + '#' + this.fragment);

¶

Return immediately as browser will do redirect to new url

            return true;

¶

Or if we've started out with a hash-based route, but we're currently in a browser where it could be `pushState`-based instead...

          } else if (this._wantsPushState && this._hasPushState && atRoot && loc.hash) {
            this.fragment = this.getHash().replace(routeStripper, '');
            window.history.replaceState({}, document.title, loc.protocol + '//' + loc.host + this.options.root + this.fragment);
          }

          if (!this.options.silent) {
            return this.loadUrl();
          }
        },

¶

Disable Backbone.history, perhaps temporarily. Not useful in a real app, but possibly useful for unit testing Routers.

        stop: function() {
          $(window).unbind('popstate', this.checkUrl).unbind('hashchange', this.checkUrl);
          clearInterval(this._checkUrlInterval);
          History.started = false;
        },

¶

Add a route to be tested when the fragment changes. Routes added later may override previous routes.

        route: function(route, callback) {
          this.handlers.unshift({route: route, callback: callback});
        },

¶

Checks the current URL to see if it has changed, and if it has, calls `loadUrl`, normalizing across the hidden iframe.

        checkUrl: function(e) {
          var current = this.getFragment();
          if (current == this.fragment && this.iframe) current = this.getFragment(this.getHash(this.iframe));
          if (current == this.fragment) return false;
          if (this.iframe) this.navigate(current);
          this.loadUrl() || this.loadUrl(this.getHash());
        },

¶

Attempt to load the current URL fragment. If a route succeeds with a match, returns `true`. If no defined routes matches the fragment, returns `false`.

        loadUrl: function(fragmentOverride) {
          var fragment = this.fragment = this.getFragment(fragmentOverride);
          var matched = _.any(this.handlers, function(handler) {
            if (handler.route.test(fragment)) {
              handler.callback(fragment);
              return true;
            }
          });
          return matched;
        },

¶

Save a fragment into the hash history, or replace the URL state if the 'replace' option is passed. You are responsible for properly URL-encoding the fragment in advance.

The options object can contain `trigger: true` if you wish to have the route callback be fired (not usually desirable), or `replace: true`, if you wish to modify the current URL without adding an entry to the history.

        navigate: function(fragment, options) {
          if (!History.started) return false;
          if (!options || options === true) options = {trigger: options};
          var frag = (fragment || '').replace(routeStripper, '');
          if (this.fragment == frag) return;

¶

If pushState is available, we use it to set the fragment as a real URL.

          if (this._hasPushState) {
            if (frag.indexOf(this.options.root) != 0) frag = this.options.root + frag;
            this.fragment = frag;
            window.history[options.replace ? 'replaceState' : 'pushState']({}, document.title, frag);

¶

If hash changes haven't been explicitly disabled, update the hash fragment to store history.

          } else if (this._wantsHashChange) {
            this.fragment = frag;
            this._updateHash(window.location, frag, options.replace);
            if (this.iframe && (frag != this.getFragment(this.getHash(this.iframe)))) {

¶

Opening and closing the iframe tricks IE7 and earlier to push a history entry on hash-tag change. When replace is true, we don't want this.

              if(!options.replace) this.iframe.document.open().close();
              this._updateHash(this.iframe.location, frag, options.replace);
            }

¶

If you've told us that you explicitly don't want fallback hashchange- based history, then `navigate` becomes a page refresh.

          } else {
            window.location.assign(this.options.root + fragment);
          }
          if (options.trigger) this.loadUrl(fragment);
        },

¶

Update the hash location, either replacing the current entry, or adding a new one to the browser history.

        _updateHash: function(location, fragment, replace) {
          if (replace) {
            location.replace(location.toString().replace(/(javascript:|#).*$/, '') + '#' + fragment);
          } else {
            location.hash = fragment;
          }
        }
      });

¶

## Backbone.View

¶

Creating a Backbone.View creates its initial element outside of the DOM, if an existing element is not provided...

      var View = Backbone.View = function(options) {
        this.cid = _.uniqueId('view');
        this._configure(options || {});
        this._ensureElement();
        this.initialize.apply(this, arguments);
        this.delegateEvents();
      };

¶

Cached regex to split keys for `delegate`.

      var delegateEventSplitter = /^(\S+)\s*(.*)$/;

¶

List of view options to be merged as properties.

      var viewOptions = ['model', 'collection', 'el', 'id', 'attributes', 'className', 'tagName'];

¶

Set up all inheritable Backbone.View properties and methods.

      _.extend(View.prototype, Events, {

¶

The default `tagName` of a View's element is `"div"`.

        tagName: 'div',

¶

jQuery delegate for element lookup, scoped to DOM elements within the current view. This should be prefered to global lookups where possible.

        $: function(selector) {
          return this.$el.find(selector);
        },

¶

Initialize is an empty function by default. Override it with your own initialization logic.

        initialize: function(){},

¶

render is the core function that your view should override, in order to populate its element (`this.el`), with the appropriate HTML. The convention is for render to always return `this`.

        render: function() {
          return this;
        },

¶

Remove this view from the DOM. Note that the view isn't present in the DOM by default, so calling this method may be a no-op.

        remove: function() {
          this.$el.remove();
          return this;
        },

¶

For small amounts of DOM Elements, where a full-blown template isn't needed, use make to manufacture elements, one at a time.

    var el = this.make('li', {'class': 'row'}, this.model.escape('title'));

        make: function(tagName, attributes, content) {
          var el = document.createElement(tagName);
          if (attributes) $(el).attr(attributes);
          if (content) $(el).html(content);
          return el;
        },

¶

Change the view's element (`this.el` property), including event re-delegation.

        setElement: function(element, delegate) {
          if (this.$el) this.undelegateEvents();
          this.$el = (element instanceof $) ? element : $(element);
          this.el = this.$el[0];
          if (delegate !== false) this.delegateEvents();
          return this;
        },

¶

Set callbacks, where `this.events` is a hash of

{"event selector": "callback"}

    {
      'mousedown .title':  'edit',
      'click .button':     'save'
      'click .open':       function(e) { ... }
    }

pairs. Callbacks will be bound to the view, with `this` set properly. Uses event delegation for efficiency. Omitting the selector binds the event to `this.el`. This only works for delegate-able events: not `focus`, `blur`, and not `change`, `submit`, and `reset` in Internet Explorer.

        delegateEvents: function(events) {
          if (!(events || (events = getValue(this, 'events')))) return;
          this.undelegateEvents();
          for (var key in events) {
            var method = events[key];
            if (!_.isFunction(method)) method = this[events[key]];
            if (!method) throw new Error('Method "' + events[key] + '" does not exist');
            var match = key.match(delegateEventSplitter);
            var eventName = match[1], selector = match[2];
            method = _.bind(method, this);
            eventName += '.delegateEvents' + this.cid;
            if (selector === '') {
              this.$el.bind(eventName, method);
            } else {
              this.$el.delegate(selector, eventName, method);
            }
          }
        },

¶

Clears all callbacks previously bound to the view with `delegateEvents`. You usually don't need to use this, but may wish to if you have multiple Backbone views attached to the same DOM element.

        undelegateEvents: function() {
          this.$el.unbind('.delegateEvents' + this.cid);
        },

¶

Performs the initial configuration of a View with a set of options. Keys with special meaning (model, collection, id, className), are attached directly to the view.

        _configure: function(options) {
          if (this.options) options = _.extend({}, this.options, options);
          for (var i = 0, l = viewOptions.length; i < l; i++) {
            var attr = viewOptions[i];
            if (options[attr]) this[attr] = options[attr];
          }
          this.options = options;
        },

¶

Ensure that the View has a DOM element to render into. If `this.el` is a string, pass it through `$()`, take the first matching element, and re-assign it to `el`. Otherwise, create an element from the `id`, `className` and `tagName` properties.

        _ensureElement: function() {
          if (!this.el) {
            var attrs = getValue(this, 'attributes') || {};
            if (this.id) attrs.id = this.id;
            if (this.className) attrs['class'] = this.className;
            this.setElement(this.make(this.tagName, attrs), false);
          } else {
            this.setElement(this.el, false);
          }
        }

      });

¶

The self-propagating extend function that Backbone classes use.

      var extend = function (protoProps, classProps) {
        var child = inherits(this, protoProps, classProps);
        child.extend = this.extend;
        return child;
      };

¶

Set up inheritance for the model, collection, and view.

      Model.extend = Collection.extend = Router.extend = View.extend = extend;

¶

## Backbone.sync

¶

Map from CRUD to HTTP for our default `Backbone.sync` implementation.

      var methodMap = {
        'create': 'POST',
        'update': 'PUT',
        'delete': 'DELETE',
        'read':   'GET'
      };

¶

Override this function to change the manner in which Backbone persists models to the server. You will be passed the type of request, and the model in question. By default, makes a RESTful Ajax request to the model's `url()`. Some possible customizations could be:

- Use `setTimeout` to batch rapid-fire updates into a single request.
- Send up the models as XML instead of JSON.
- Persist models via WebSockets instead of Ajax.

Turn on `Backbone.emulateHTTP` in order to send `PUT` and `DELETE` requests as `POST`, with a `_method` parameter containing the true HTTP method, as well as all requests with the body as `application/x-www-form-urlencoded` instead of `application/json` with the model in a param named `model`. Useful when interfacing with server-side languages like PHP that make it difficult to read the body of `PUT` requests.

      Backbone.sync = function(method, model, options) {
        var type = methodMap[method];

¶

Default options, unless specified.

        options || (options = {});

¶

Default JSON-request options.

        var params = {type: type, dataType: 'json'};

¶

Ensure that we have a URL.

        if (!options.url) {
          params.url = getValue(model, 'url') || urlError();
        }

¶

Ensure that we have the appropriate request data.

        if (!options.data && model && (method == 'create' || method == 'update')) {
          params.contentType = 'application/json';
          params.data = JSON.stringify(model.toJSON());
        }

¶

For older servers, emulate JSON by encoding the request into an HTML-form.

        if (Backbone.emulateJSON) {
          params.contentType = 'application/x-www-form-urlencoded';
          params.data = params.data ? {model: params.data} : {};
        }

¶

For older servers, emulate HTTP by mimicking the HTTP method with `_method` And an `X-HTTP-Method-Override` header.

        if (Backbone.emulateHTTP) {
          if (type === 'PUT' || type === 'DELETE') {
            if (Backbone.emulateJSON) params.data._method = type;
            params.type = 'POST';
            params.beforeSend = function(xhr) {
              xhr.setRequestHeader('X-HTTP-Method-Override', type);
            };
          }
        }

¶

Don't process data on a non-GET request.

        if (params.type !== 'GET' && !Backbone.emulateJSON) {
          params.processData = false;
        }

¶

Make the request, allowing the user to override any Ajax options.

        return $.ajax(_.extend(params, options));
      };

¶

Wrap an optional error callback with a fallback error event.

      Backbone.wrapError = function(onError, originalModel, options) {
        return function(model, resp) {
          resp = model === originalModel ? resp : model;
          if (onError) {
            onError(originalModel, resp, options);
          } else {
            originalModel.trigger('error', originalModel, resp, options);
          }
        };
      };

¶

## Helpers

¶

Shared empty constructor function to aid in prototype-chain creation.

      var ctor = function(){};

¶

Helper function to correctly set up the prototype chain, for subclasses. Similar to `goog.inherits`, but uses a hash of prototype properties and class properties to be extended.

      var inherits = function(parent, protoProps, staticProps) {
        var child;

¶

The constructor function for the new subclass is either defined by you (the "constructor" property in your `extend` definition), or defaulted by us to simply call the parent's constructor.

        if (protoProps && protoProps.hasOwnProperty('constructor')) {
          child = protoProps.constructor;
        } else {
          child = function(){ parent.apply(this, arguments); };
        }

¶

Inherit class (static) properties from parent.

        _.extend(child, parent);

¶

Set the prototype chain to inherit from `parent`, without calling `parent`'s constructor function.

        ctor.prototype = parent.prototype;
        child.prototype = new ctor();

¶

Add prototype properties (instance properties) to the subclass, if supplied.

        if (protoProps) _.extend(child.prototype, protoProps);

¶

Add static properties to the constructor function, if supplied.

        if (staticProps) _.extend(child, staticProps);

¶

Correctly set child's `prototype.constructor`.

        child.prototype.constructor = child;

¶

Set a convenience property in case the parent's prototype is needed later.

        child.__super__ = parent.prototype;

        return child;
      };

¶

Helper function to get a value from a Backbone object as a property or as a function.

      var getValue = function(object, prop) {
        if (!(object && object[prop])) return null;
        return _.isFunction(object[prop]) ? object[prop]() : object[prop];
      };

¶

Throw an error when a URL is needed, and none is supplied.

      var urlError = function() {
        throw new Error('A "url" property or function must be specified');
      };

    }).call(this);