backebone源码

//     Backbone.js 1.1.2

// (c) 2010-2014 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
// Backbone may be freely distributed under the MIT license.
// For all details and documentation:
// http://backbonejs.org

(function(root, factory) {

// Set up Backbone appropriately for the environment. Start with AMD.
if (typeof define === 'function' && define.amd) {
define(['underscore', 'jquery', 'exports'], function(_, $, exports) {
// Export global even in AMD case in case this script is loaded with
// others that may still expect a global Backbone.
root.Backbone = factory(root, exports, _, $);
});

// Next for Node.js or CommonJS. jQuery may not be needed as a module.
} else if (typeof exports !== 'undefined') {
var _ = require('underscore');
factory(root, exports, _);

// Finally, as a browser global.
} else {
root.Backbone = factory(root, {}, root._, (root.jQuery || root.Zepto || root.ender || root.$));
}

}(this, function(root, Backbone, _, $) {

// Initial Setup
// -------------

// 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 local references to array methods we'll want to use later.
var array = [];
var push = array.push;
var slice = array.slice;
var splice = array.splice;

// Current version of the library. Keep in sync with package.json.
Backbone.VERSION = '1.1.2';

// For Backbone's purposes, jQuery, Zepto, Ender, or My Library (kidding) owns
// the $ variable.
Backbone.$ = $;

// 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 "PATCH", "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 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 an event to a `callback` function. Passing `"all"` will bind
// the callback to all events fired.
on: function(name, callback, context) {
  if (!eventsApi(this, 'on', name, [callback, context]) || !callback) return this;
  this._events || (this._events = {});
  var events = this._events[name] || (this._events[name] = []);
  events.push({callback: callback, context: context, ctx: context || this});
  return this;
},

// Bind an event to only be triggered a single time. After the first time
// the callback is invoked, it will be removed.
once: function(name, callback, context) {
  if (!eventsApi(this, 'once', name, [callback, context]) || !callback) return this;
  var self = this;
  var once = _.once(function() {
    self.off(name, once);
    callback.apply(this, arguments);
  });
  once._callback = callback;
  return this.on(name, once, context);
},

// 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 `name` is null, removes all bound
// callbacks for all events.
off: function(name, callback, context) {
  var retain, ev, events, names, i, l, j, k;
  if (!this._events || !eventsApi(this, 'off', name, [callback, context])) return this;
  if (!name && !callback && !context) {
    this._events = void 0;
    return this;
  }
  names = name ? [name] : _.keys(this._events);
  for (i = 0, l = names.length; i < l; i++) {
    name = names[i];
    if (events = this._events[name]) {
      this._events[name] = retain = [];
      if (callback || context) {
        for (j = 0, k = events.length; j < k; j++) {
          ev = events[j];
          if ((callback && callback !== ev.callback && callback !== ev.callback._callback) ||
              (context && context !== ev.context)) {
            retain.push(ev);
          }
        }
      }
      if (!retain.length) delete this._events[name];
    }
  }

  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(name) {
  if (!this._events) return this;
  var args = slice.call(arguments, 1);
  if (!eventsApi(this, 'trigger', name, args)) return this;
  var events = this._events[name];
  var allEvents = this._events.all;
  if (events) triggerEvents(events, args);
  if (allEvents) triggerEvents(allEvents, arguments);
  return this;
},

// Tell this object to stop listening to either specific events ... or
// to every object it's currently listening to.
stopListening: function(obj, name, callback) {
  var listeningTo = this._listeningTo;
  if (!listeningTo) return this;
  var remove = !name && !callback;
  if (!callback && typeof name === 'object') callback = this;
  if (obj) (listeningTo = {})[obj._listenId] = obj;
  for (var id in listeningTo) {
    obj = listeningTo[id];
    obj.off(name, callback, this);
    if (remove || _.isEmpty(obj._events)) delete this._listeningTo[id];
  }
  return this;
}

};

// Regular expression used to split event strings.
var eventSplitter = /\s+/;

// Implement fancy features of the Events API such as multiple event
// names "change blur" and jQuery-style event maps {change: action}
// in terms of the existing API.
var eventsApi = function(obj, action, name, rest) {
if (!name) return true;

// Handle event maps.
if (typeof name === 'object') {
  for (var key in name) {
    obj[action].apply(obj, [key, name[key]].concat(rest));
  }
  return false;
}

// Handle space separated event names.
if (eventSplitter.test(name)) {
  var names = name.split(eventSplitter);
  for (var i = 0, l = names.length; i < l; i++) {
    obj[action].apply(obj, [names[i]].concat(rest));
  }
  return false;
}

return true;

};

// A difficult-to-believe, but optimized internal dispatch function for
// triggering events. Tries to keep the usual cases speedy (most internal
// Backbone events have 3 arguments).
var triggerEvents = function(events, args) {
var ev, i = -1, l = events.length, a1 = args[0], a2 = args[1], a3 = args[2];
switch (args.length) {
case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx); return;
case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1); return;
case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2); return;
case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2, a3); return;
default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args); return;
}
};

var listenMethods = {listenTo: 'on', listenToOnce: 'once'};

// Inversion-of-control versions of on and once. Tell this object to
// listen to an event in another object ... keeping track of what it's
// listening to.
_.each(listenMethods, function(implementation, method) {
Events[method] = function(obj, name, callback) {
var listeningTo = this._listeningTo || (this._listeningTo = {});
var id = obj._listenId || (obj._listenId = _.uniqueId('l'));
listeningTo[id] = obj;
if (!callback && typeof name === 'object') callback = this;
obj[implementation](name, callback, this);
return this;
};
});

// Aliases for backwards compatibility.
Events.bind = Events.on;
Events.unbind = Events.off;

// Allow the Backbone object to serve as a global event bus, for folks who
// want global "pubsub" in a convenient place.
_.extend(Backbone, Events);

// Backbone.Model
// --------------

// Backbone Models are the basic data object in the framework --
// frequently representing a row in a table in a database on your server.
// A discrete chunk of data and a bunch of useful, related methods for
// performing computations and transformations on that data.

// Create a new model with the specified attributes. A client id (cid)
// is automatically generated and assigned for you.
var Model = Backbone.Model = function(attributes, options) {
var attrs = attributes || {};
options || (options = {});
this.cid = _.uniqueId('c');
this.attributes = {};
if (options.collection) this.collection = options.collection;
if (options.parse) attrs = this.parse(attrs, options) || {};
attrs = _.defaults({}, attrs, _.result(this, 'defaults'));
this.set(attrs, options);
this.changed = {};
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,

// The value returned during the last failed validation.
validationError: 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);
},

// Proxy `Backbone.sync` by default -- but override this if you need
// custom syncing semantics for *this* particular model.
sync: function() {
  return Backbone.sync.apply(this, arguments);
},

// Get the value of an attribute.
get: function(attr) {
  return this.attributes[attr];
},

// Get the HTML-escaped value of an attribute.
escape: function(attr) {
  return _.escape(this.get(attr));
},

// 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"`. This is
// the core primitive operation of a model, updating the data and notifying
// anyone who needs to know about the change in state. The heart of the beast.
set: function(key, val, options) {
  var attr, attrs, unset, changes, silent, changing, prev, current;
  if (key == null) return this;

  // Handle both `"key", value` and `{key: value}` -style arguments.
  if (typeof key === 'object') {
    attrs = key;
    options = val;
  } else {
    (attrs = {})[key] = val;
  }

  options || (options = {});

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

  // Extract attributes and options.
  unset           = options.unset;
  silent          = options.silent;
  changes         = [];
  changing        = this._changing;
  this._changing  = true;

  if (!changing) {
    this._previousAttributes = _.clone(this.attributes);
    this.changed = {};
  }
  current = this.attributes, prev = this._previousAttributes;

  // Check for changes of `id`.
  if (this.idAttribute in attrs) this.id = attrs[this.idAttribute];

  // For each `set` attribute, update or delete the current value.
  for (attr in attrs) {
    val = attrs[attr];
    if (!_.isEqual(current[attr], val)) changes.push(attr);
    if (!_.isEqual(prev[attr], val)) {
      this.changed[attr] = val;
    } else {
      delete this.changed[attr];
    }
    unset ? delete current[attr] : current[attr] = val;
  }

  // Trigger all relevant attribute changes.
  if (!silent) {
    if (changes.length) this._pending = options;
    for (var i = 0, l = changes.length; i < l; i++) {
      this.trigger('change:' + changes[i], this, current[changes[i]], options);
    }
  }

  // You might be wondering why there's a `while` loop here. Changes can
  // be recursively nested within `"change"` events.
  if (changing) return this;
  if (!silent) {
    while (this._pending) {
      options = this._pending;
      this._pending = false;
      this.trigger('change', this, options);
    }
  }
  this._pending = false;
  this._changing = false;
  return this;
},

// Remove an attribute from the model, firing `"change"`. `unset` is a noop
// if the attribute doesn't exist.
unset: function(attr, options) {
  return this.set(attr, void 0, _.extend({}, options, {unset: true}));
},

// Clear all attributes on the model, firing `"change"`.
clear: function(options) {
  var attrs = {};
  for (var key in this.attributes) attrs[key] = void 0;
  return this.set(attrs, _.extend({}, options, {unset: true}));
},

// 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 == null) 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;
  var old = this._changing ? this._previousAttributes : this.attributes;
  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 (attr == null || !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);
},

// Fetch the model from the server. If the server's representation of the
// model differs from its current attributes, they will be overridden,
// triggering a `"change"` event.
fetch: function(options) {
  options = options ? _.clone(options) : {};
  if (options.parse === void 0) options.parse = true;
  var model = this;
  var success = options.success;
  options.success = function(resp) {
    if (!model.set(model.parse(resp, options), options)) return false;
    if (success) success(model, resp, options);
    model.trigger('sync', model, resp, options);
  };
  wrapError(this, options);
  return this.sync('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, val, options) {
  var attrs, method, xhr, attributes = this.attributes;

  // Handle both `"key", value` and `{key: value}` -style arguments.
  if (key == null || typeof key === 'object') {
    attrs = key;
    options = val;
  } else {
    (attrs = {})[key] = val;
  }

  options = _.extend({validate: true}, options);

  // If we're not waiting and attributes exist, save acts as
  // `set(attr).save(null, opts)` with validation. Otherwise, check if
  // the model will be valid when the attributes, if any, are set.
  if (attrs && !options.wait) {
    if (!this.set(attrs, options)) return false;
  } else {
    if (!this._validate(attrs, options)) return false;
  }

  // Set temporary attributes if `{wait: true}`.
  if (attrs && options.wait) {
    this.attributes = _.extend({}, attributes, attrs);
  }

  // After a successful server-side save, the client is (optionally)
  // updated with the server-side state.
  if (options.parse === void 0) options.parse = true;
  var model = this;
  var success = options.success;
  options.success = function(resp) {
    // Ensure attributes are restored during synchronous saves.
    model.attributes = attributes;
    var serverAttrs = model.parse(resp, options);
    if (options.wait) serverAttrs = _.extend(attrs || {}, serverAttrs);
    if (_.isObject(serverAttrs) && !model.set(serverAttrs, options)) {
      return false;
    }
    if (success) success(model, resp, options);
    model.trigger('sync', model, resp, options);
  };
  wrapError(this, options);

  method = this.isNew() ? 'create' : (options.patch ? 'patch' : 'update');
  if (method === 'patch') options.attrs = attrs;
  xhr = this.sync(method, this, options);

  // Restore attributes.
  if (attrs && options.wait) this.attributes = attributes;

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

  options.success = function(resp) {
    if (options.wait || model.isNew()) destroy();
    if (success) success(model, resp, options);
    if (!model.isNew()) model.trigger('sync', model, resp, options);
  };

  if (this.isNew()) {
    options.success();
    return false;
  }
  wrapError(this, options);

  var xhr = this.sync('delete', this, options);
  if (!options.wait) destroy();
  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 =
    _.result(this, 'urlRoot') ||
    _.result(this.collection, 'url') ||
    urlError();
  if (this.isNew()) return base;
  return base.replace(/([^\/])$/, '$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, options) {
  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.has(this.idAttribute);
},

// Check if the model is currently in a valid state.
isValid: function(options) {
  return this._validate({}, _.extend(options || {}, { validate: true }));
},

// Run validation against the next complete set of model attributes,
// returning `true` if all is well. Otherwise, fire an `"invalid"` event.
_validate: function(attrs, options) {
  if (!options.validate || !this.validate) return true;
  attrs = _.extend({}, this.attributes, attrs);
  var error = this.validationError = this.validate(attrs, options) || null;
  if (!error) return true;
  this.trigger('invalid', this, error, _.extend(options, {validationError: error}));
  return false;
}

});

// Underscore methods that we want to implement on the Model.
var modelMethods = ['keys', 'values', 'pairs', 'invert', 'pick', 'omit'];

// Mix in each Underscore method as a proxy to Model#attributes.
.each(modelMethods, function(method) {
Model.prototype[method] = function() {
var args = slice.call(arguments);
args.unshift(this.attributes);
return _[method].apply(, args);
};
});

// Backbone.Collection
// -------------------

// If models tend to represent a single row of data, a Backbone Collection is
// more analagous to a table full of data ... or a small slice or page of that
// table, or a collection of rows that belong together for a particular reason
// -- all of the messages in this particular folder, all of the documents
// belonging to this particular author, and so on. Collections maintain
// indexes of their models, both in order, and for lookup by id.

// Create a new Collection, perhaps to contain a specific type of model.
// 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 !== void 0) this.comparator = options.comparator;
this._reset();
this.initialize.apply(this, arguments);
if (models) this.reset(models, _.extend({silent: true}, options));
};

// Default options for Collection#set.
var setOptions = {add: true, remove: true, merge: true};
var addOptions = {add: true, remove: false};

// 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); });
},

// Proxy `Backbone.sync` by default.
sync: function() {
  return Backbone.sync.apply(this, arguments);
},

// Add a model, or list of models to the set.
add: function(models, options) {
  return this.set(models, _.extend({merge: false}, options, addOptions));
},

// Remove a model, or a list of models from the set.
remove: function(models, options) {
  var singular = !_.isArray(models);
  models = singular ? [models] : _.clone(models);
  options || (options = {});
  var i, l, index, model;
  for (i = 0, l = models.length; i < l; i++) {
    model = models[i] = this.get(models[i]);
    if (!model) continue;
    delete this._byId[model.id];
    delete this._byId[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, options);
  }
  return singular ? models[0] : models;
},

// Update a collection by `set`-ing a new list of models, adding new ones,
// removing models that are no longer present, and merging models that
// already exist in the collection, as necessary. Similar to **Model#set**,
// the core operation for updating the data contained by the collection.
set: function(models, options) {
  options = _.defaults({}, options, setOptions);
  if (options.parse) models = this.parse(models, options);
  var singular = !_.isArray(models);
  models = singular ? (models ? [models] : []) : _.clone(models);
  var i, l, id, model, attrs, existing, sort;
  var at = options.at;
  var targetModel = this.model;
  var sortable = this.comparator && (at == null) && options.sort !== false;
  var sortAttr = _.isString(this.comparator) ? this.comparator : null;
  var toAdd = [], toRemove = [], modelMap = {};
  var add = options.add, merge = options.merge, remove = options.remove;
  var order = !sortable && add && remove ? [] : false;

  // Turn bare objects into model references, and prevent invalid models
  // from being added.
  for (i = 0, l = models.length; i < l; i++) {
    attrs = models[i] || {};
    if (attrs instanceof Model) {
      id = model = attrs;
    } else {
      id = attrs[targetModel.prototype.idAttribute || 'id'];
    }

    // If a duplicate is found, prevent it from being added and
    // optionally merge it into the existing model.
    if (existing = this.get(id)) {
      if (remove) modelMap[existing.cid] = true;
      if (merge) {
        attrs = attrs === model ? model.attributes : attrs;
        if (options.parse) attrs = existing.parse(attrs, options);
        existing.set(attrs, options);
        if (sortable && !sort && existing.hasChanged(sortAttr)) sort = true;
      }
      models[i] = existing;

    // If this is a new, valid model, push it to the `toAdd` list.
    } else if (add) {
      model = models[i] = this._prepareModel(attrs, options);
      if (!model) continue;
      toAdd.push(model);
      this._addReference(model, options);
    }

    // Do not add multiple models with the same `id`.
    model = existing || model;
    if (order && (model.isNew() || !modelMap[model.id])) order.push(model);
    modelMap[model.id] = true;
  }

  // Remove nonexistent models if appropriate.
  if (remove) {
    for (i = 0, l = this.length; i < l; ++i) {
      if (!modelMap[(model = this.models[i]).cid]) toRemove.push(model);
    }
    if (toRemove.length) this.remove(toRemove, options);
  }

  // See if sorting is needed, update `length` and splice in new models.
  if (toAdd.length || (order && order.length)) {
    if (sortable) sort = true;
    this.length += toAdd.length;
    if (at != null) {
      for (i = 0, l = toAdd.length; i < l; i++) {
        this.models.splice(at + i, 0, toAdd[i]);
      }
    } else {
      if (order) this.models.length = 0;
      var orderedModels = order || toAdd;
      for (i = 0, l = orderedModels.length; i < l; i++) {
        this.models.push(orderedModels[i]);
      }
    }
  }

  // Silently sort the collection if appropriate.
  if (sort) this.sort({silent: true});

  // Unless silenced, it's time to fire all appropriate add/sort events.
  if (!options.silent) {
    for (i = 0, l = toAdd.length; i < l; i++) {
      (model = toAdd[i]).trigger('add', model, this, options);
    }
    if (sort || (order && order.length)) this.trigger('sort', this, options);
  }

  // Return the added (or merged) model (or models).
  return singular ? models[0] : models;
},

// 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 granular `add` or `remove` events. Fires `reset` when finished.
// Useful for bulk operations and optimizations.
reset: function(models, options) {
  options || (options = {});
  for (var i = 0, l = this.models.length; i < l; i++) {
    this._removeReference(this.models[i], options);
  }
  options.previousModels = this.models;
  this._reset();
  models = this.add(models, _.extend({silent: true}, options));
  if (!options.silent) this.trigger('reset', this, options);
  return models;
},

// Add a model to the end of the collection.
push: function(model, options) {
  return this.add(model, _.extend({at: this.length}, options));
},

// 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) {
  return this.add(model, _.extend({at: 0}, options));
},

// Remove a model from the beginning of the collection.
shift: function(options) {
  var model = this.at(0);
  this.remove(model, options);
  return model;
},

// Slice out a sub-array of models from the collection.
slice: function() {
  return slice.apply(this.models, arguments);
},

// Get a model from the set by id.
get: function(obj) {
  if (obj == null) return void 0;
  return this._byId[obj] || this._byId[obj.id] || this._byId[obj.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, first) {
  if (_.isEmpty(attrs)) return first ? void 0 : [];
  return this[first ? 'find' : 'filter'](function(model) {
    for (var key in attrs) {
      if (attrs[key] !== model.get(key)) return false;
    }
    return true;
  });
},

// Return the first model with matching attributes. Useful for simple cases
// of `find`.
findWhere: function(attrs) {
  return this.where(attrs, 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) {
  if (!this.comparator) throw new Error('Cannot sort a set without a comparator');
  options || (options = {});

  // Run sort based on type of `comparator`.
  if (_.isString(this.comparator) || this.comparator.length === 1) {
    this.models = this.sortBy(this.comparator, this);
  } else {
    this.models.sort(_.bind(this.comparator, this));
  }

  if (!options.silent) this.trigger('sort', this, options);
  return this;
},

// Pluck an attribute from each model in the collection.
pluck: function(attr) {
  return _.invoke(this.models, 'get', attr);
},

// Fetch the default set of models for this collection, resetting the
// collection when they arrive. If `reset: true` is passed, the response
// data will be passed through the `reset` method instead of `set`.
fetch: function(options) {
  options = options ? _.clone(options) : {};
  if (options.parse === void 0) options.parse = true;
  var success = options.success;
  var collection = this;
  options.success = function(resp) {
    var method = options.reset ? 'reset' : 'set';
    collection[method](resp, options);
    if (success) success(collection, resp, options);
    collection.trigger('sync', collection, resp, options);
  };
  wrapError(this, options);
  return this.sync('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) {
  options = options ? _.clone(options) : {};
  if (!(model = this._prepareModel(model, options))) return false;
  if (!options.wait) this.add(model, options);
  var collection = this;
  var success = options.success;
  options.success = function(model, resp) {
    if (options.wait) collection.add(model, options);
    if (success) success(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, options) {
  return resp;
},

// Create a new collection with an identical list of models as this one.
clone: function() {
  return new this.constructor(this.models);
},

// Private method to reset all internal state. Called when the collection
// is first initialized or reset.
_reset: function() {
  this.length = 0;
  this.models = [];
  this._byId  = {};
},

// Prepare a hash of attributes (or other model) to be added to this
// collection.
_prepareModel: function(attrs, options) {
  if (attrs instanceof Model) return attrs;
  options = options ? _.clone(options) : {};
  options.collection = this;
  var model = new this.model(attrs, options);
  if (!model.validationError) return model;
  this.trigger('invalid', this, model.validationError, options);
  return false;
},

// Internal method to create a model's ties to a collection.
_addReference: function(model, options) {
  this._byId[model.cid] = model;
  if (model.id != null) this._byId[model.id] = model;
  if (!model.collection) model.collection = this;
  model.on('all', this._onModelEvent, this);
},

// Internal method to sever a model's ties to a collection.
_removeReference: function(model, options) {
  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)];
    if (model.id != null) this._byId[model.id] = model;
  }
  this.trigger.apply(this, arguments);
}

});

// Underscore methods that we want to implement on the Collection.
// 90% of the core usefulness of Backbone Collections is actually implemented
// right here:
var methods = ['forEach', 'each', 'map', 'collect', 'reduce', 'foldl',
'inject', 'reduceRight', 'foldr', 'find', 'detect', 'filter', 'select',
'reject', 'every', 'all', 'some', 'any', 'include', 'contains', 'invoke',
'max', 'min', 'toArray', 'size', 'first', 'head', 'take', 'initial', 'rest',
'tail', 'drop', 'last', 'without', 'difference', 'indexOf', 'shuffle',
'lastIndexOf', 'isEmpty', 'chain', 'sample'];

// Mix in each Underscore method as a proxy to Collection#models.
.each(methods, function(method) {
Collection.prototype[method] = function() {
var args = slice.call(arguments);
args.unshift(this.models);
return _[method].apply(, args);
};
});

// Underscore methods that take a property name as an argument.
var attributeMethods = ['groupBy', 'countBy', 'sortBy', 'indexBy'];

// Use attributes instead of properties.
_.each(attributeMethods, function(method) {
Collection.prototype[method] = function(value, context) {
var iterator = _.isFunction(value) ? value : function(model) {
return model.get(value);
};
return _[method](this.models, iterator, context);
};
});

// Backbone.View
// -------------

// Backbone Views are almost more convention than they are actual code. A View
// is simply a JavaScript object that represents a logical chunk of UI in the
// DOM. This might be a single item, an entire list, a sidebar or panel, or
// even the surrounding frame which wraps your whole app. Defining a chunk of
// UI as a View allows you to define your DOM events declaratively, without
// having to worry about render order ... and makes it easy for the view to
// react to specific changes in the state of your models.

// 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');
options || (options = {});
_.extend(this, _.pick(options, viewOptions));
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', 'events'];

// 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 preferred 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 by taking the element out of the DOM, and removing any
// applicable Backbone.Events listeners.
remove: function() {
  this.$el.remove();
  this.stopListening();
  return this;
},

// 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 Backbone.$ ? element : Backbone.$(element);
  this.el = this.$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 = _.result(this, 'events')))) return this;
  this.undelegateEvents();
  for (var key in events) {
    var method = events[key];
    if (!_.isFunction(method)) method = this[events[key]];
    if (!method) continue;

    var match = key.match(delegateEventSplitter);
    var eventName = match[1], selector = match[2];
    method = _.bind(method, this);
    eventName += '.delegateEvents' + this.cid;
    if (selector === '') {
      this.$el.on(eventName, method);
    } else {
      this.$el.on(eventName, selector, method);
    }
  }
  return this;
},

// 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.off('.delegateEvents' + this.cid);
  return this;
},

// 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 = _.extend({}, _.result(this, 'attributes'));
    if (this.id) attrs.id = _.result(this, 'id');
    if (this.className) attrs['class'] = _.result(this, 'className');
    var $el = Backbone.$('<' + _.result(this, 'tagName') + '>').attr(attrs);
    this.setElement($el, false);
  } else {
    this.setElement(_.result(this, 'el'), false);
  }
}

});

// 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, 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.
_.defaults(options || (options = {}), {
  emulateHTTP: Backbone.emulateHTTP,
  emulateJSON: Backbone.emulateJSON
});

// Default JSON-request options.
var params = {type: type, dataType: 'json'};

// Ensure that we have a URL.
if (!options.url) {
  params.url = _.result(model, 'url') || urlError();
}

// Ensure that we have the appropriate request data.
if (options.data == null && model && (method === 'create' || method === 'update' || method === 'patch')) {
  params.contentType = 'application/json';
  params.data = JSON.stringify(options.attrs || model.toJSON(options));
}

// For older servers, emulate JSON by encoding the request into an HTML-form.
if (options.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 (options.emulateHTTP && (type === 'PUT' || type === 'DELETE' || type === 'PATCH')) {
  params.type = 'POST';
  if (options.emulateJSON) params.data._method = type;
  var beforeSend = options.beforeSend;
  options.beforeSend = function(xhr) {
    xhr.setRequestHeader('X-HTTP-Method-Override', type);
    if (beforeSend) return beforeSend.apply(this, arguments);
  };
}

// Don't process data on a non-GET request.
if (params.type !== 'GET' && !options.emulateJSON) {
  params.processData = false;
}

// If we're sending a `PATCH` request, and we're in an old Internet Explorer
// that still has ActiveX enabled by default, override jQuery to use that
// for XHR instead. Remove this line when jQuery supports `PATCH` on IE8.
if (params.type === 'PATCH' && noXhrPatch) {
  params.xhr = function() {
    return new ActiveXObject("Microsoft.XMLHTTP");
  };
}

// Make the request, allowing the user to override any Ajax options.
var xhr = options.xhr = Backbone.ajax(_.extend(params, options));
model.trigger('request', model, xhr, options);
return xhr;

};

var noXhrPatch =
typeof window !== 'undefined' && !!window.ActiveXObject &&
!(window.XMLHttpRequest && (new XMLHttpRequest).dispatchEvent);

// Map from CRUD to HTTP for our default Backbone.sync implementation.
var methodMap = {
'create': 'POST',
'update': 'PUT',
'patch': 'PATCH',
'delete': 'DELETE',
'read': 'GET'
};

// Set the default implementation of Backbone.ajax to proxy through to $.
// Override this if you'd like to use a different library.
Backbone.ajax = function() {
return Backbone.$.ajax.apply(Backbone.$, 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 optionalParam = /((.*?))/g;
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) {
  if (!_.isRegExp(route)) route = this._routeToRegExp(route);
  if (_.isFunction(name)) {
    callback = name;
    name = '';
  }
  if (!callback) callback = this[name];
  var router = this;
  Backbone.history.route(route, function(fragment) {
    var args = router._extractParameters(route, fragment);
    router.execute(callback, args);
    router.trigger.apply(router, ['route:' + name].concat(args));
    router.trigger('route', name, args);
    Backbone.history.trigger('route', router, name, args);
  });
  return this;
},

// Execute a route handler with the provided parameters.  This is an
// excellent place to do pre-route setup or post-route cleanup.
execute: function(callback, args) {
  if (callback) callback.apply(this, args);
},

// Simple proxy to `Backbone.history` to save a fragment into the history.
navigate: function(fragment, options) {
  Backbone.history.navigate(fragment, options);
  return this;
},

// 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;
  this.routes = _.result(this, 'routes');
  var route, routes = _.keys(this.routes);
  while ((route = routes.pop()) != null) {
    this.route(route, this.routes[route]);
  }
},

// Convert a route string into a regular expression, suitable for matching
// against the current location hash.
_routeToRegExp: function(route) {
  route = route.replace(escapeRegExp, '\\$&')
               .replace(optionalParam, '(?:$1)?')
               .replace(namedParam, function(match, optional) {
                 return optional ? match : '([^/?]+)';
               })
               .replace(splatParam, '([^?]*?)');
  return new RegExp('^' + route + '(?:\\?([\\s\\S]*))?$');
},

// Given a route, and a URL fragment that it matches, return the array of
// extracted decoded parameters. Empty or unmatched parameters will be
// treated as `null` to normalize cross-browser behavior.
_extractParameters: function(route, fragment) {
  var params = route.exec(fragment).slice(1);
  return _.map(params, function(param, i) {
    // Don't decode the search params.
    if (i === params.length - 1) return param || null;
    return param ? decodeURIComponent(param) : null;
  });
}

});

// Backbone.History
// ----------------

// Handles cross-browser history management, based on either
// pushState and real URLs, or
// onhashchange
// and URL fragments. If the browser supports neither (old IE, natch),
// falls back to polling.
var History = Backbone.History = function() {
this.handlers = [];
_.bindAll(this, 'checkUrl');

// Ensure that `History` can be used outside of the browser.
if (typeof window !== 'undefined') {
  this.location = window.location;
  this.history = window.history;
}

};

// Cached regex for stripping a leading hash/slash and trailing space.
var routeStripper = /^[#\/]|\s+$/g;

// Cached regex for stripping leading and trailing slashes.
var rootStripper = /^\/+|\/+$/g;

// Cached regex for detecting MSIE.
var isExplorer = /msie [\w.]+/;

// Cached regex for removing a trailing slash.
var trailingSlash = /\/$/;

// Cached regex for stripping urls of hash.
var pathStripper = /#.*$/;

// 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,

// Are we at the app root?
atRoot: function() {
  return this.location.pathname.replace(/[^\/]$/, '$&/') === this.root;
},

// Gets the true hash value. Cannot use location.hash directly due to bug
// in Firefox where location.hash will always be decoded.
getHash: function(window) {
  var match = (window || this).location.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 || !this._wantsHashChange || forcePushState) {
      fragment = decodeURI(this.location.pathname + this.location.search);
      var root = this.root.replace(trailingSlash, '');
      if (!fragment.indexOf(root)) fragment = fragment.slice(root.length);
    } else {
      fragment = this.getHash();
    }
  }
  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.root             = this.options.root;
  this._wantsHashChange = this.options.hashChange !== false;
  this._wantsPushState  = !!this.options.pushState;
  this._hasPushState    = !!(this.options.pushState && this.history && this.history.pushState);
  var fragment          = this.getFragment();
  var docMode           = document.documentMode;
  var oldIE             = (isExplorer.exec(navigator.userAgent.toLowerCase()) && (!docMode || docMode <= 7));

  // Normalize root to always include a leading and trailing slash.
  this.root = ('/' + this.root + '/').replace(rootStripper, '/');

  if (oldIE && this._wantsHashChange) {
    var frame = Backbone.$('<iframe src="javascript:0" tabindex="-1">');
    this.iframe = frame.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) {
    Backbone.$(window).on('popstate', this.checkUrl);
  } else if (this._wantsHashChange && ('onhashchange' in window) && !oldIE) {
    Backbone.$(window).on('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 = this.location;

  // Transition from hashChange to pushState or vice versa if both are
  // requested.
  if (this._wantsHashChange && this._wantsPushState) {

    // 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._hasPushState && !this.atRoot()) {
      this.fragment = this.getFragment(null, true);
      this.location.replace(this.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._hasPushState && this.atRoot() && loc.hash) {
      this.fragment = this.getHash().replace(routeStripper, '');
      this.history.replaceState({}, document.title, this.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() {
  Backbone.$(window).off('popstate', this.checkUrl).off('hashchange', this.checkUrl);
  if (this._checkUrlInterval) 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();
},

// 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(fragment) {
  fragment = this.fragment = this.getFragment(fragment);
  return _.any(this.handlers, function(handler) {
    if (handler.route.test(fragment)) {
      handler.callback(fragment);
      return true;
    }
  });
},

// 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 url = this.root + (fragment = this.getFragment(fragment || ''));

  // Strip the hash for matching.
  fragment = fragment.replace(pathStripper, '');

  if (this.fragment === fragment) return;
  this.fragment = fragment;

  // Don't include a trailing slash on the root.
  if (fragment === '' && url !== '/') url = url.slice(0, -1);

  // If pushState is available, we use it to set the fragment as a real URL.
  if (this._hasPushState) {
    this.history[options.replace ? 'replaceState' : 'pushState']({}, document.title, url);

  // If hash changes haven't been explicitly disabled, update the hash
  // fragment to store history.
  } else if (this._wantsHashChange) {
    this._updateHash(this.location, fragment, options.replace);
    if (this.iframe && (fragment !== 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, fragment, options.replace);
    }

  // If you've told us that you explicitly don't want fallback hashchange-
  // based history, then `navigate` becomes a page refresh.
  } else {
    return this.location.assign(url);
  }
  if (options.trigger) return 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) {
    var href = location.href.replace(/(javascript:|#).*$/, '');
    location.replace(href + '#' + fragment);
  } else {
    // Some browsers require that `hash` contains a leading #.
    location.hash = '#' + fragment;
  }
}

});

// Create the default Backbone.history.
Backbone.history = new History;

// Helpers
// -------

// 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 extend = function(protoProps, staticProps) {
var parent = this;
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 && _.has(protoProps, 'constructor')) {
  child = protoProps.constructor;
} else {
  child = function(){ return parent.apply(this, arguments); };
}

// Add static properties to the constructor function, if supplied.
_.extend(child, parent, staticProps);

// Set the prototype chain to inherit from `parent`, without calling
// `parent`'s constructor function.
var Surrogate = function(){ this.constructor = child; };
Surrogate.prototype = parent.prototype;
child.prototype = new Surrogate;

// Add prototype properties (instance properties) to the subclass,
// if supplied.
if (protoProps) _.extend(child.prototype, protoProps);

// Set a convenience property in case the parent's prototype is needed
// later.
child.__super__ = parent.prototype;

return child;

};

// Set up inheritance for the model, collection, router, view and history.
Model.extend = Collection.extend = Router.extend = View.extend = History.extend = extend;

// 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');
};

// Wrap an optional error callback with a fallback error event.
var wrapError = function(model, options) {
var error = options.error;
options.error = function(resp) {
if (error) error(model, resp, options);
model.trigger('error', model, resp, options);
};
};

return Backbone;

}));