# backbone.js

¶

    Backbone.js 0.3.3
    (c) 2010 Jeremy Ashkenas, DocumentCloud Inc.
    Backbone may be freely distributed under the MIT license.
    For all details and documentation:
    http://documentcloud.github.com/backbone

    (function(){

¶

## Initial Setup

¶

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 = this.Backbone = {};
      }

¶

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

      Backbone.VERSION = '0.3.3';

¶

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

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

¶

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

      var $ = this.jQuery || this.Zepto;

¶

Turn on `emulateHTTP` to use 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

¶

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

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

      Backbone.Events = {

¶

Bind an event, specified by a string name, `ev`, to a `callback` function. Passing `"all"` will bind the callback to all events fired.

        bind : function(ev, callback) {
          var calls = this._callbacks || (this._callbacks = {});
          var list  = this._callbacks[ev] || (this._callbacks[ev] = []);
          list.push(callback);
          return this;
        },

¶

Remove one or many callbacks. If `callback` is null, removes all callbacks for the event. If `ev` is null, removes all bound callbacks for all events.

        unbind : function(ev, callback) {
          var calls;
          if (!ev) {
            this._callbacks = {};
          } else if (calls = this._callbacks) {
            if (!callback) {
              calls[ev] = [];
            } else {
              var list = calls[ev];
              if (!list) return this;
              for (var i = 0, l = list.length; i < l; i++) {
                if (callback === list[i]) {
                  list.splice(i, 1);
                  break;
                }
              }
            }
          }
          return this;
        },

¶

Trigger an event, firing all bound callbacks. Callbacks are passed the same arguments as `trigger` is, apart from the event name. Listening for `"all"` passes the true event name as the first argument.

        trigger : function(ev) {
          var list, calls, i, l;
          if (!(calls = this._callbacks)) return this;
          if (list = calls[ev]) {
            for (i = 0, l = list.length; i < l; i++) {
              list[i].apply(this, Array.prototype.slice.call(arguments, 1));
            }
          }
          if (list = calls['all']) {
            for (i = 0, l = list.length; i < l; i++) {
              list[i].apply(this, arguments);
            }
          }
          return this;
        }

      };

¶

## Backbone.Model

¶

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

      Backbone.Model = function(attributes, options) {
        attributes || (attributes = {});
        if (this.defaults) attributes = _.extend({}, this.defaults, attributes);
        this.attributes = {};
        this._escapedAttributes = {};
        this.cid = _.uniqueId('c');
        this.set(attributes, {silent : true});
        this._previousAttributes = _.clone(this.attributes);
        if (options && options.collection) this.collection = options.collection;
        this.initialize(attributes, options);
      };

¶

Attach all inheritable methods to the Model prototype.

      _.extend(Backbone.Model.prototype, Backbone.Events, {

¶

A snapshot of the model's previous attributes, taken immediately after the last `"change"` event was fired.

        _previousAttributes : null,

¶

Has the item been changed since the last `"change"` event?

        _changed : false,

¶

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() {
          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.attributes[attr];
          return this._escapedAttributes[attr] = escapeHTML(val == null ? '' : val);
        },

¶

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

        set : function(attrs, options) {

¶

Extract attributes and options.

          options || (options = {});
          if (!attrs) return this;
          if (attrs.attributes) attrs = attrs.attributes;
          var now = this.attributes, escaped = this._escapedAttributes;

¶

Run validation.

          if (!options.silent && this.validate && !this._performValidation(attrs, options)) return false;

¶

Check for changes of `id`.

          if ('id' in attrs) this.id = attrs.id;

¶

Update attributes.

          for (var attr in attrs) {
            var val = attrs[attr];
            if (!_.isEqual(now[attr], val)) {
              now[attr] = val;
              delete escaped[attr];
              if (!options.silent) {
                this._changed = true;
                this.trigger('change:' + attr, this, val, options);
              }
            }
          }

¶

Fire the `"change"` event, if the model has been changed.

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

¶

Remove an attribute from the model, firing `"change"` unless you choose to silence it.

        unset : function(attr, options) {
          options || (options = {});
          var value = this.attributes[attr];

¶

Run validation.

          var validObj = {};
          validObj[attr] = void 0;
          if (!options.silent && this.validate && !this._performValidation(validObj, options)) return false;

¶

Remove the attribute.

          delete this.attributes[attr];
          delete this._escapedAttributes[attr];
          if (!options.silent) {
            this._changed = true;
            this.trigger('change:' + attr, this, void 0, options);
            this.change(options);
          }
          return this;
        },

¶

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

        clear : function(options) {
          options || (options = {});
          var old = this.attributes;

¶

Run validation.

          var validObj = {};
          for (attr in old) validObj[attr] = void 0;
          if (!options.silent && this.validate && !this._performValidation(validObj, options)) return false;

          this.attributes = {};
          this._escapedAttributes = {};
          if (!options.silent) {
            this._changed = true;
            for (attr in old) {
              this.trigger('change:' + attr, this, void 0, options);
            }
            this.change(options);
          }
          return this;
        },

¶

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 = {});
          var model = this;
          var success = function(resp) {
            if (!model.set(model.parse(resp), options)) return false;
            if (options.success) options.success(model, resp);
          };
          var error = wrapError(options.error, model, options);
          (this.sync || Backbone.sync)('read', this, success, error);
          return this;
        },

¶

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(attrs, options) {
          options || (options = {});
          if (attrs && !this.set(attrs, options)) return false;
          var model = this;
          var success = function(resp) {
            if (!model.set(model.parse(resp), options)) return false;
            if (options.success) options.success(model, resp);
          };
          var error = wrapError(options.error, model, options);
          var method = this.isNew() ? 'create' : 'update';
          (this.sync || Backbone.sync)(method, this, success, error);
          return this;
        },

¶

Destroy this model on the server. Upon success, the model is removed from its collection, if it has one.

        destroy : function(options) {
          options || (options = {});
          var model = this;
          var success = function(resp) {
            if (model.collection) model.collection.remove(model);
            if (options.success) options.success(model, resp);
          };
          var error = wrapError(options.error, model, options);
          (this.sync || Backbone.sync)('delete', this, success, error);
          return this;
        },

¶

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 = getUrl(this.collection);
          if (this.isNew()) return base;
          return base + (base.charAt(base.length - 1) == '/' ? '' : '/') + 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) {
          return resp;
        },

¶

Create a new model with identical attributes to this one.

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

¶

A model is new if it has never been saved to the server, and has a negative ID.

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

¶

Call this method to manually fire a `change` event for this model. Calling this will cause all objects observing the model to update.

        change : function(options) {
          this.trigger('change', this, options);
          this._previousAttributes = _.clone(this.attributes);
          this._changed = false;
        },

¶

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 (attr) return this._previousAttributes[attr] != this.attributes[attr];
          return this._changed;
        },

¶

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.

        changedAttributes : function(now) {
          now || (now = this.attributes);
          var old = this._previousAttributes;
          var changed = false;
          for (var attr in now) {
            if (!_.isEqual(old[attr], now[attr])) {
              changed = changed || {};
              changed[attr] = now[attr];
            }
          }
          return changed;
        },

¶

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

        previous : function(attr) {
          if (!attr || !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);
        },

¶

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

        _performValidation : function(attrs, options) {
          var error = this.validate(attrs);
          if (error) {
            if (options.error) {
              options.error(this, error);
            } else {
              this.trigger('error', this, error, options);
            }
            return false;
          }
          return true;
        }

      });

¶

## 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.

      Backbone.Collection = function(models, options) {
        options || (options = {});
        if (options.comparator) {
          this.comparator = options.comparator;
          delete options.comparator;
        }
        this._boundOnModelEvent = _.bind(this._onModelEvent, this);
        this._reset();
        if (models) this.refresh(models, {silent: true});
        this.initialize(models, options);
      };

¶

Define the Collection's inheritable methods.

      _.extend(Backbone.Collection.prototype, Backbone.Events, {

¶

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

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

¶

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

        add : function(models, options) {
          if (_.isArray(models)) {
            for (var i = 0, l = models.length; i < l; i++) {
              this._add(models[i], options);
            }
          } else {
            this._add(models, options);
          }
          return this;
        },

¶

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

        remove : function(models, options) {
          if (_.isArray(models)) {
            for (var i = 0, l = models.length; i < l; i++) {
              this._remove(models[i], options);
            }
          } else {
            this._remove(models, options);
          }
          return this;
        },

¶

Get a model from the set by id.

        get : function(id) {
          if (id == null) return null;
          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];
        },

¶

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');
          this.models = this.sortBy(this.comparator);
          if (!options.silent) this.trigger('refresh', 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 refresh the entire set with a new list of models, without firing any `added` or `removed` events. Fires `refresh` when finished.

        refresh : function(models, options) {
          models  || (models = []);
          options || (options = {});
          this._reset();
          this.add(models, {silent: true});
          if (!options.silent) this.trigger('refresh', this, options);
          return this;
        },

¶

Fetch the default set of models for this collection, refreshing the collection when they arrive.

        fetch : function(options) {
          options || (options = {});
          var collection = this;
          var success = function(resp) {
            collection.refresh(collection.parse(resp));
            if (options.success) options.success(collection, resp);
          };
          var error = wrapError(options.error, collection, options);
          (this.sync || Backbone.sync)('read', this, success, error);
          return this;
        },

¶

Create a new instance of a model in this collection. After the model has been created on the server, it will be added to the collection.

        create : function(model, options) {
          var coll = this;
          options || (options = {});
          if (!(model instanceof Backbone.Model)) {
            model = new this.model(model, {collection: coll});
          } else {
            model.collection = coll;
          }
          var success = function(nextModel, resp) {
            coll.add(nextModel);
            if (options.success) options.success(nextModel, resp);
          };
          return model.save(null, {success : success, error : options.error});
        },

¶

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) {
          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 refreshed.

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

¶

Internal implementation of adding a single model to the set, updating hash indexes for `id` and `cid` lookups.

        _add : function(model, options) {
          options || (options = {});
          if (!(model instanceof Backbone.Model)) {
            model = new this.model(model, {collection: this});
          }
          var already = this.getByCid(model);
          if (already) throw new Error(["Can't add the same model to a set twice", already.id]);
          this._byId[model.id] = model;
          this._byCid[model.cid] = model;
          model.collection = this;
          var index = this.comparator ? this.sortedIndex(model, this.comparator) : this.length;
          this.models.splice(index, 0, model);
          model.bind('all', this._boundOnModelEvent);
          this.length++;
          if (!options.silent) model.trigger('add', model, this, options);
          return model;
        },

¶

Internal implementation of removing a single model from the set, updating hash indexes for `id` and `cid` lookups.

        _remove : function(model, options) {
          options || (options = {});
          model = this.getByCid(model) || this.get(model);
          if (!model) return null;
          delete this._byId[model.id];
          delete this._byCid[model.cid];
          delete model.collection;
          this.models.splice(this.indexOf(model), 1);
          this.length--;
          if (!options.silent) model.trigger('remove', model, this, options);
          model.unbind('all', this._boundOnModelEvent);
          return model;
        },

¶

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.

        _onModelEvent : function(ev, model) {
          if (ev === 'change:id') {
            delete this._byId[model.previous('id')];
            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',
        'invoke', 'max', 'min', 'sortBy', 'sortedIndex', 'toArray', 'size',
        'first', 'rest', 'last', 'without', 'indexOf', 'lastIndexOf', 'isEmpty'];

¶

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

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

¶

## Backbone.Controller

¶

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

      Backbone.Controller = function(options) {
        options || (options = {});
        if (options.routes) this.routes = options.routes;
        this._bindRoutes();
        this.initialize(options);
      };

¶

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

      var namedParam = /:([\w\d]+)/g;
      var splatParam = /\*([\w\d]+)/g;

¶

Set up all inheritable Backbone.Controller properties and methods.

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

¶

Simple proxy to `Backbone.history` to save a fragment into the history, without triggering routes.

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

¶

Bind all defined routes to `Backbone.history`.

        _bindRoutes : function() {
          if (!this.routes) return;
          for (var route in this.routes) {
            var name = this.routes[route];
            this.route(route, name, this[name]);
          }
        },

¶

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

        _routeToRegExp : function(route) {
          route = route.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 hashes. If the browser does not support `onhashchange`, falls back to polling.

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

¶

Cached regex for cleaning hashes.

      var hashStrip = /^#*/;

¶

Set up all inheritable Backbone.History properties and methods.

      _.extend(Backbone.History.prototype, {

¶

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

        interval: 50,

¶

Get the cross-browser normalized URL fragment.

        getFragment : function(loc) {
          return (loc || window.location).hash.replace(hashStrip, '');
        },

¶

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

        start : function() {
          var docMode = document.documentMode;
          var oldIE = ($.browser.msie && (!docMode || docMode <= 7));
          if (oldIE) {
            this.iframe = $('<iframe src="javascript:0" tabindex="-1" />').hide().appendTo('body')[0].contentWindow;
          }
          if ('onhashchange' in window && !oldIE) {
            $(window).bind('hashchange', this.checkUrl);
          } else {
            setInterval(this.checkUrl, this.interval);
          }
          return this.loadUrl();
        },

¶

Add a route to be tested when the hash changes. Routes are matched in the order they are added.

        route : function(route, callback) {
          this.handlers.push({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() {
          var current = this.getFragment();
          if (current == this.fragment && this.iframe) {
            current = this.getFragment(this.iframe.location);
          }
          if (current == this.fragment ||
              current == decodeURIComponent(this.fragment)) return false;
          if (this.iframe) {
            window.location.hash = this.iframe.location.hash = current;
          }
          this.loadUrl();
        },

¶

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() {
          var fragment = this.fragment = this.getFragment();
          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. You are responsible for properly URL-encoding the fragment in advance. This does not trigger a `hashchange` event.

        saveLocation : function(fragment) {
          fragment = (fragment || '').replace(hashStrip, '');
          if (this.fragment == fragment) return;
          window.location.hash = this.fragment = fragment;
          if (this.iframe && (fragment != this.getFragment(this.iframe.location))) {
            this.iframe.document.open().close();
            this.iframe.location.hash = fragment;
          }
        }

      });

¶

## Backbone.View

¶

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

      Backbone.View = function(options) {
        this._configure(options || {});
        this._ensureElement();
        this.delegateEvents();
        this.initialize(options);
      };

¶

Element lookup, scoped to DOM elements within the current view. This should be prefered to global lookups, if you're dealing with a specific view.

      var selectorDelegate = function(selector) {
        return $(selector, this.el);
      };

¶

Cached regex to split keys for `delegate`.

      var eventSplitter = /^(\w+)\s*(.*)$/;

¶

Set up all inheritable Backbone.View properties and methods.

      _.extend(Backbone.View.prototype, Backbone.Events, {

¶

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

        tagName : 'div',

¶

Attach the `selectorDelegate` function as the `$` property.

        $       : selectorDelegate,

¶

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.get('title'));

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

¶

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

{"event selector": "callback"}

    {
      'mousedown .title':  'edit',
      'click .button':     'save'
    }

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 = this.events))) return;
          $(this.el).unbind();
          for (var key in events) {
            var methodName = events[key];
            var match = key.match(eventSplitter);
            var eventName = match[1], selector = match[2];
            var method = _.bind(this[methodName], this);
            if (selector === '') {
              $(this.el).bind(eventName, method);
            } else {
              $(this.el).delegate(selector, eventName, method);
            }
          }
        },

¶

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);
          if (options.model)      this.model      = options.model;
          if (options.collection) this.collection = options.collection;
          if (options.el)         this.el         = options.el;
          if (options.id)         this.id         = options.id;
          if (options.className)  this.className  = options.className;
          if (options.tagName)    this.tagName    = options.tagName;
          this.options = options;
        },

¶

Ensure that the View has a DOM element to render into.

        _ensureElement : function() {
          if (this.el) return;
          var attrs = {};
          if (this.id) attrs.id = this.id;
          if (this.className) attrs["class"] = this.className;
          this.el = this.make(this.tagName, attrs);
        }

      });

¶

The self-propagating extend function that Backbone classes use.

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

¶

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

      Backbone.Model.extend = Backbone.Collection.extend =
        Backbone.Controller.extend = Backbone.View.extend = extend;

¶

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

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

¶

## Backbone.sync

¶

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, uses 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, success, error) {
        var type = methodMap[method];
        var modelJSON = (method === 'create' || method === 'update') ?
                        JSON.stringify(model.toJSON()) : null;

¶

Default JSON-request options.

        var params = {
          url:          getUrl(model),
          type:         type,
          contentType:  'application/json',
          data:         modelJSON,
          dataType:     'json',
          processData:  false,
          success:      success,
          error:        error
        };

¶

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

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

¶

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);
            };
          }
        }

¶

Make the request.

        $.ajax(params);
      };

¶

## 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 `super()`.

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

¶

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`, for `instanceof`.

        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 URL from a Model or Collection as a property or as a function.

      var getUrl = function(object) {
        if (!(object && object.url)) throw new Error("A 'url' property or function must be specified");
        return _.isFunction(object.url) ? object.url() : object.url;
      };

¶

Wrap an optional error callback with a fallback error event.

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

¶

Helper function to escape a string for HTML rendering.

      var escapeHTML = function(string) {
        return string.replace(/&(?!\w+;)/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
      };

    })();