backbone.js

(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.

  var Backbone = {};

Keep the version here in sync with package.json.

  Backbone.VERSION = '0.1.0';

Export for both CommonJS and the browser.

  (typeof exports !== 'undefined' ? exports : this).Backbone = Backbone;

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

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

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, classProps) {
    var child = protoProps.hasOwnProperty('constructor') ? protoProps.constructor :
                function(){ return parent.apply(this, arguments); };
    var ctor = function(){};
    ctor.prototype = parent.prototype;
    child.prototype = new ctor();
    _.extend(child.prototype, protoProps);
    if (classProps) _.extend(child, classProps);
    child.prototype.constructor = child;
    return child;
  };

Helper function to get a URL from a Model or Collection as a property or as a function.

  var getUrl = function(object) {
    return _.isFunction(object.url) ? object.url() : object.url;
  };

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;
      var calls = this._callbacks;
      if (!(calls = this._callbacks)) return this;
      if (list = calls[ev]) {
        for (i = 0, l = list.length; i < l; i++) {
          list[i].apply(this, _.rest(arguments));
        }
      }
      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) {
    this.attributes = {};
    this.cid = _.uniqueId('c');
    this.set(attributes || {}, {silent : true});
    this._previousAttributes = _.clone(this.attributes);
  };

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 changed event was fired.

    _previousAttributes : null,

Has the item been changed since the last changed event?

    _changed : false,

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];
    },

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

    set : function(attrs, options) {

Extract attributes and options.

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

Run validation if validate is defined.

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

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

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

Remove an attribute from the model, firing changed unless you choose to silence it.

    unset : function(attr, options) {
      options || (options = {});
      var value = this.attributes[attr];
      delete this.attributes[attr];
      if (!options.silent) {
        this._changed = true;
        this.trigger('change:' + attr, this);
        this.change();
      }
      return value;
    },

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) {
      attrs   || (attrs = {});
      options || (options = {});
      if (!this.set(attrs, options)) return false;
      var model = this;
      var success = function(resp) {
        if (!model.set(resp.model)) return false;
        if (options.success) options.success(model, resp);
      };
      var method = this.isNew() ? 'create' : 'update';
      Backbone.sync(method, this, success, options.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);
      };
      Backbone.sync('delete', this, success, options.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 + '/' + this.id;
    },

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

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

Determine if the model has changed since the last changed 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) {
      var old = this._previousAttributes, now = now || this.attributes, 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 changed 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 changed event.

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

  });

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._initialize();
    if (models) this.refresh(models,true);
  };

Define the Collection's inheritable methods.

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

    model : Backbone.Model,

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)) return this._add(models, options);
      for (var i=0; i<models.length; i++) this._add(models[i], options);
      return models;
    },

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)) return this._remove(models, options);
      for (var i=0; i<models.length; i++) this._remove(models[i], options);
      return models;
    },

Get a model from the set by id.

    get : function(id) {
      return id && 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);
      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) {
      options || (options = {});
      models = models || [];
      var collection = this;
      if (models[0] && !(models[0] instanceof Backbone.Model)) {
        models = _.map(models, function(attrs, i) {
          return new collection.model(attrs);
        });
      }
      this._initialize();
      this.add(models, {silent: true});
      if (!options.silent) this.trigger('refresh', this);
      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(resp.models);
        if (options.success) options.success(collection, resp);
      };
      Backbone.sync('read', this, success, options.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) {
      options || (options = {});
      if (!(model instanceof Backbone.Model)) model = new this.model(model);
      model.collection = this;
      var success = function(resp) {
        if (!model.set(resp.model)) return false;
        model.collection.add(model);
        if (options.success) options.success(model, resp);
      };
      return model.save(null, {success : success, error : options.error});
    },

Initialize or re-initialize all internal state. Called when the collection is refreshed.

    _initialize : 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 = {});
      var already = this.get(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) this.trigger('add', model);
      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.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);
      model.unbind('all', this._boundOnModelEvent);
      this.length--;
      if (!options.silent) this.trigger('remove', model);
      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.

    _onModelEvent : function(ev, model, error) {
      switch (ev) {
        case 'change':
          if (model.hasChanged('id')) {
            delete this._byId[model.previous('id')];
            this._byId[model.id] = model;
          }
          this.trigger('change', model);
          break;
        case 'error':
          this.trigger('error', model, error);
      }
    }

  });

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.View

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

  Backbone.View = function(options) {
    this._initialize(options || {});
    if (this.options.el) {
      this.el = this.options.el;
    } else {
      var attrs = {};
      if (this.id) attrs.id = this.id;
      if (this.className) attrs.className = this.className;
      this.el = this.make(this.tagName, attrs);
    }
    return this;
  };

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

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

Cached regex to split keys for handleEvents.

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

Set up all inheritable Backbone.View properties and methods.

  _.extend(Backbone.View.prototype, {

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

    tagName : 'div',

Attach the jQuery function as the $ and jQuery properties.

    $       : jQueryDelegate,
    jQuery  : jQueryDelegate,

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;
    },

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 jQuery event delegation for efficiency. Omitting the selector binds the event to this.el. "change" events are not delegated through the view because IE does not bubble change events at all.

    handleEvents : function(events) {
      $(this.el).unbind();
      if (!(events || (events = this.events))) return this;
      for (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 === '' || eventName == 'change') {
          $(this.el).bind(eventName, method);
        } else {
          $(this.el).delegate(selector, eventName, method);
        }
      }
      return this;
    },

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.

    _initialize : 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.id)         this.id         = options.id;
      if (options.className)  this.className  = options.className;
      if (options.tagName)    this.tagName    = options.tagName;
      this.options = options;
    }

  });

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

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

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, uses jQuery to make 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.
  Backbone.sync = function(method, model, success, error) {
    $.ajax({
      url       : getUrl(model),
      type      : methodMap[method],
      data      : {model : JSON.stringify(model)},
      dataType  : 'json',
      success   : success,
      error     : error
    });
  };

})();