1//     Backbone.js 1.3.3
2
3//     (c) 2010-2016 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
4//     Backbone may be freely distributed under the MIT license.
5//     For all details and documentation:
6//     http://backbonejs.org
7
8(function(factory) {
9
10  // Establish the root object, `window` (`self`) in the browser, or `global` on the server.
11  // We use `self` instead of `window` for `WebWorker` support.
12  var root = (typeof self == 'object' && self.self === self && self) ||
13            (typeof global == 'object' && global.global === global && global);
14
15  // Set up Backbone appropriately for the environment. Start with AMD.
16  if (typeof define === 'function' && define.amd) {
17    define(['underscore', 'jquery', 'exports'], function(_, $, exports) {
18      // Export global even in AMD case in case this script is loaded with
19      // others that may still expect a global Backbone.
20      root.Backbone = factory(root, exports, _, $);
21    });
22
23  // Next for Node.js or CommonJS. jQuery may not be needed as a module.
24  } else if (typeof exports !== 'undefined') {
25    var _ = require('underscore'), $;
26    try { $ = require('jquery'); } catch (e) {}
27    factory(root, exports, _, $);
28
29  // Finally, as a browser global.
30  } else {
31    root.Backbone = factory(root, {}, root._, (root.jQuery || root.Zepto || root.ender || root.$));
32  }
33
34})(function(root, Backbone, _, $) {
35
36  // Initial Setup
37  // -------------
38
39  // Save the previous value of the `Backbone` variable, so that it can be
40  // restored later on, if `noConflict` is used.
41  var previousBackbone = root.Backbone;
42
43  // Create a local reference to a common array method we'll want to use later.
44  var slice = Array.prototype.slice;
45
46  // Current version of the library. Keep in sync with `package.json`.
47  Backbone.VERSION = '1.3.3';
48
49  // For Backbone's purposes, jQuery, Zepto, Ender, or My Library (kidding) owns
50  // the `$` variable.
51  Backbone.$ = $;
52
53  // Runs Backbone.js in *noConflict* mode, returning the `Backbone` variable
54  // to its previous owner. Returns a reference to this Backbone object.
55  Backbone.noConflict = function() {
56    root.Backbone = previousBackbone;
57    return this;
58  };
59
60  // Turn on `emulateHTTP` to support legacy HTTP servers. Setting this option
61  // will fake `"PATCH"`, `"PUT"` and `"DELETE"` requests via the `_method` parameter and
62  // set a `X-Http-Method-Override` header.
63  Backbone.emulateHTTP = false;
64
65  // Turn on `emulateJSON` to support legacy servers that can't deal with direct
66  // `application/json` requests ... this will encode the body as
67  // `application/x-www-form-urlencoded` instead and will send the model in a
68  // form param named `model`.
69  Backbone.emulateJSON = false;
70
71  // Proxy Backbone class methods to Underscore functions, wrapping the model's
72  // `attributes` object or collection's `models` array behind the scenes.
73  //
74  // collection.filter(function(model) { return model.get('age') > 10 });
75  // collection.each(this.addView);
76  //
77  // `Function#apply` can be slow so we use the method's arg count, if we know it.
78  var addMethod = function(length, method, attribute) {
79    switch (length) {
80      case 1: return function() {
81        return _[method](this[attribute]);
82      };
83      case 2: return function(value) {
84        return _[method](this[attribute], value);
85      };
86      case 3: return function(iteratee, context) {
87        return _[method](this[attribute], cb(iteratee, this), context);
88      };
89      case 4: return function(iteratee, defaultVal, context) {
90        return _[method](this[attribute], cb(iteratee, this), defaultVal, context);
91      };
92      default: return function() {
93        var args = slice.call(arguments);
94        args.unshift(this[attribute]);
95        return _[method].apply(_, args);
96      };
97    }
98  };
99  var addUnderscoreMethods = function(Class, methods, attribute) {
100    _.each(methods, function(length, method) {
101      if (_[method]) Class.prototype[method] = addMethod(length, method, attribute);
102    });
103  };
104
105  // Support `collection.sortBy('attr')` and `collection.findWhere({id: 1})`.
106  var cb = function(iteratee, instance) {
107    if (_.isFunction(iteratee)) return iteratee;
108    if (_.isObject(iteratee) && !instance._isModel(iteratee)) return modelMatcher(iteratee);
109    if (_.isString(iteratee)) return function(model) { return model.get(iteratee); };
110    return iteratee;
111  };
112  var modelMatcher = function(attrs) {
113    var matcher = _.matches(attrs);
114    return function(model) {
115      return matcher(model.attributes);
116    };
117  };
118
119  // Backbone.Events
120  // ---------------
121
122  // A module that can be mixed in to *any object* in order to provide it with
123  // a custom event channel. You may bind a callback to an event with `on` or
124  // remove with `off`; `trigger`-ing an event fires all callbacks in
125  // succession.
126  //
127  //     var object = {};
128  //     _.extend(object, Backbone.Events);
129  //     object.on('expand', function(){ alert('expanded'); });
130  //     object.trigger('expand');
131  //
132  var Events = Backbone.Events = {};
133
134  // Regular expression used to split event strings.
135  var eventSplitter = /\s+/;
136
137  // Iterates over the standard `event, callback` (as well as the fancy multiple
138  // space-separated events `"change blur", callback` and jQuery-style event
139  // maps `{event: callback}`).
140  var eventsApi = function(iteratee, events, name, callback, opts) {
141    var i = 0, names;
142    if (name && typeof name === 'object') {
143      // Handle event maps.
144      if (callback !== void 0 && 'context' in opts && opts.context === void 0) opts.context = callback;
145      for (names = _.keys(name); i < names.length ; i++) {
146        events = eventsApi(iteratee, events, names[i], name[names[i]], opts);
147      }
148    } else if (name && eventSplitter.test(name)) {
149      // Handle space-separated event names by delegating them individually.
150      for (names = name.split(eventSplitter); i < names.length; i++) {
151        events = iteratee(events, names[i], callback, opts);
152      }
153    } else {
154      // Finally, standard events.
155      events = iteratee(events, name, callback, opts);
156    }
157    return events;
158  };
159
160  // Bind an event to a `callback` function. Passing `"all"` will bind
161  // the callback to all events fired.
162  Events.on = function(name, callback, context) {
163    return internalOn(this, name, callback, context);
164  };
165
166  // Guard the `listening` argument from the public API.
167  var internalOn = function(obj, name, callback, context, listening) {
168    obj._events = eventsApi(onApi, obj._events || {}, name, callback, {
169      context: context,
170      ctx: obj,
171      listening: listening
172    });
173
174    if (listening) {
175      var listeners = obj._listeners || (obj._listeners = {});
176      listeners[listening.id] = listening;
177    }
178
179    return obj;
180  };
181
182  // Inversion-of-control versions of `on`. Tell *this* object to listen to
183  // an event in another object... keeping track of what it's listening to
184  // for easier unbinding later.
185  Events.listenTo = function(obj, name, callback) {
186    if (!obj) return this;
187    var id = obj._listenId || (obj._listenId = _.uniqueId('l'));
188    var listeningTo = this._listeningTo || (this._listeningTo = {});
189    var listening = listeningTo[id];
190
191    // This object is not listening to any other events on `obj` yet.
192    // Setup the necessary references to track the listening callbacks.
193    if (!listening) {
194      var thisId = this._listenId || (this._listenId = _.uniqueId('l'));
195      listening = listeningTo[id] = {obj: obj, objId: id, id: thisId, listeningTo: listeningTo, count: 0};
196    }
197
198    // Bind callbacks on obj, and keep track of them on listening.
199    internalOn(obj, name, callback, this, listening);
200    return this;
201  };
202
203  // The reducing API that adds a callback to the `events` object.
204  var onApi = function(events, name, callback, options) {
205    if (callback) {
206      var handlers = events[name] || (events[name] = []);
207      var context = options.context, ctx = options.ctx, listening = options.listening;
208      if (listening) listening.count++;
209
210      handlers.push({callback: callback, context: context, ctx: context || ctx, listening: listening});
211    }
212    return events;
213  };
214
215  // Remove one or many callbacks. If `context` is null, removes all
216  // callbacks with that function. If `callback` is null, removes all
217  // callbacks for the event. If `name` is null, removes all bound
218  // callbacks for all events.
219  Events.off = function(name, callback, context) {
220    if (!this._events) return this;
221    this._events = eventsApi(offApi, this._events, name, callback, {
222      context: context,
223      listeners: this._listeners
224    });
225    return this;
226  };
227
228  // Tell this object to stop listening to either specific events ... or
229  // to every object it's currently listening to.
230  Events.stopListening = function(obj, name, callback) {
231    var listeningTo = this._listeningTo;
232    if (!listeningTo) return this;
233
234    var ids = obj ? [obj._listenId] : _.keys(listeningTo);
235
236    for (var i = 0; i < ids.length; i++) {
237      var listening = listeningTo[ids[i]];
238
239      // If listening doesn't exist, this object is not currently
240      // listening to obj. Break out early.
241      if (!listening) break;
242
243      listening.obj.off(name, callback, this);
244    }
245
246    return this;
247  };
248
249  // The reducing API that removes a callback from the `events` object.
250  var offApi = function(events, name, callback, options) {
251    if (!events) return;
252
253    var i = 0, listening;
254    var context = options.context, listeners = options.listeners;
255
256    // Delete all events listeners and "drop" events.
257    if (!name && !callback && !context) {
258      var ids = _.keys(listeners);
259      for (; i < ids.length; i++) {
260        listening = listeners[ids[i]];
261        delete listeners[listening.id];
262        delete listening.listeningTo[listening.objId];
263      }
264      return;
265    }
266
267    var names = name ? [name] : _.keys(events);
268    for (; i < names.length; i++) {
269      name = names[i];
270      var handlers = events[name];
271
272      // Bail out if there are no events stored.
273      if (!handlers) break;
274
275      // Replace events if there are any remaining.  Otherwise, clean up.
276      var remaining = [];
277      for (var j = 0; j < handlers.length; j++) {
278        var handler = handlers[j];
279        if (
280          callback && callback !== handler.callback &&
281            callback !== handler.callback._callback ||
282              context && context !== handler.context
283        ) {
284          remaining.push(handler);
285        } else {
286          listening = handler.listening;
287          if (listening && --listening.count === 0) {
288            delete listeners[listening.id];
289            delete listening.listeningTo[listening.objId];
290          }
291        }
292      }
293
294      // Update tail event if the list has any events.  Otherwise, clean up.
295      if (remaining.length) {
296        events[name] = remaining;
297      } else {
298        delete events[name];
299      }
300    }
301    return events;
302  };
303
304  // Bind an event to only be triggered a single time. After the first time
305  // the callback is invoked, its listener will be removed. If multiple events
306  // are passed in using the space-separated syntax, the handler will fire
307  // once for each event, not once for a combination of all events.
308  Events.once = function(name, callback, context) {
309    // Map the event into a `{event: once}` object.
310    var events = eventsApi(onceMap, {}, name, callback, _.bind(this.off, this));
311    if (typeof name === 'string' && context == null) callback = void 0;
312    return this.on(events, callback, context);
313  };
314
315  // Inversion-of-control versions of `once`.
316  Events.listenToOnce = function(obj, name, callback) {
317    // Map the event into a `{event: once}` object.
318    var events = eventsApi(onceMap, {}, name, callback, _.bind(this.stopListening, this, obj));
319    return this.listenTo(obj, events);
320  };
321
322  // Reduces the event callbacks into a map of `{event: onceWrapper}`.
323  // `offer` unbinds the `onceWrapper` after it has been called.
324  var onceMap = function(map, name, callback, offer) {
325    if (callback) {
326      var once = map[name] = _.once(function() {
327        offer(name, once);
328        callback.apply(this, arguments);
329      });
330      once._callback = callback;
331    }
332    return map;
333  };
334
335  // Trigger one or many events, firing all bound callbacks. Callbacks are
336  // passed the same arguments as `trigger` is, apart from the event name
337  // (unless you're listening on `"all"`, which will cause your callback to
338  // receive the true name of the event as the first argument).
339  Events.trigger = function(name) {
340    if (!this._events) return this;
341
342    var length = Math.max(0, arguments.length - 1);
343    var args = Array(length);
344    for (var i = 0; i < length; i++) args[i] = arguments[i + 1];
345
346    eventsApi(triggerApi, this._events, name, void 0, args);
347    return this;
348  };
349
350  // Handles triggering the appropriate event callbacks.
351  var triggerApi = function(objEvents, name, callback, args) {
352    if (objEvents) {
353      var events = objEvents[name];
354      var allEvents = objEvents.all;
355      if (events && allEvents) allEvents = allEvents.slice();
356      if (events) triggerEvents(events, args);
357      if (allEvents) triggerEvents(allEvents, [name].concat(args));
358    }
359    return objEvents;
360  };
361
362  // A difficult-to-believe, but optimized internal dispatch function for
363  // triggering events. Tries to keep the usual cases speedy (most internal
364  // Backbone events have 3 arguments).
365  var triggerEvents = function(events, args) {
366    var ev, i = -1, l = events.length, a1 = args[0], a2 = args[1], a3 = args[2];
367    switch (args.length) {
368      case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx); return;
369      case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1); return;
370      case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2); return;
371      case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2, a3); return;
372      default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args); return;
373    }
374  };
375
376  // Aliases for backwards compatibility.
377  Events.bind   = Events.on;
378  Events.unbind = Events.off;
379
380  // Allow the `Backbone` object to serve as a global event bus, for folks who
381  // want global "pubsub" in a convenient place.
382  _.extend(Backbone, Events);
383
384  // Backbone.Model
385  // --------------
386
387  // Backbone **Models** are the basic data object in the framework --
388  // frequently representing a row in a table in a database on your server.
389  // A discrete chunk of data and a bunch of useful, related methods for
390  // performing computations and transformations on that data.
391
392  // Create a new model with the specified attributes. A client id (`cid`)
393  // is automatically generated and assigned for you.
394  var Model = Backbone.Model = function(attributes, options) {
395    var attrs = attributes || {};
396    options || (options = {});
397    this.preinitialize.apply(this, arguments);
398    this.cid = _.uniqueId(this.cidPrefix);
399    this.attributes = {};
400    if (options.collection) this.collection = options.collection;
401    if (options.parse) attrs = this.parse(attrs, options) || {};
402    var defaults = _.result(this, 'defaults');
403    attrs = _.defaults(_.extend({}, defaults, attrs), defaults);
404    this.set(attrs, options);
405    this.changed = {};
406    this.initialize.apply(this, arguments);
407  };
408
409  // Attach all inheritable methods to the Model prototype.
410  _.extend(Model.prototype, Events, {
411
412    // A hash of attributes whose current and previous value differ.
413    changed: null,
414
415    // The value returned during the last failed validation.
416    validationError: null,
417
418    // The default name for the JSON `id` attribute is `"id"`. MongoDB and
419    // CouchDB users may want to set this to `"_id"`.
420    idAttribute: 'id',
421
422    // The prefix is used to create the client id which is used to identify models locally.
423    // You may want to override this if you're experiencing name clashes with model ids.
424    cidPrefix: 'c',
425
426    // preinitialize is an empty function by default. You can override it with a function
427    // or object.  preinitialize will run before any instantiation logic is run in the Model.
428    preinitialize: function(){},
429
430    // Initialize is an empty function by default. Override it with your own
431    // initialization logic.
432    initialize: function(){},
433
434    // Return a copy of the model's `attributes` object.
435    toJSON: function(options) {
436      return _.clone(this.attributes);
437    },
438
439    // Proxy `Backbone.sync` by default -- but override this if you need
440    // custom syncing semantics for *this* particular model.
441    sync: function() {
442      return Backbone.sync.apply(this, arguments);
443    },
444
445    // Get the value of an attribute.
446    get: function(attr) {
447      return this.attributes[attr];
448    },
449
450    // Get the HTML-escaped value of an attribute.
451    escape: function(attr) {
452      return _.escape(this.get(attr));
453    },
454
455    // Returns `true` if the attribute contains a value that is not null
456    // or undefined.
457    has: function(attr) {
458      return this.get(attr) != null;
459    },
460
461    // Special-cased proxy to underscore's `_.matches` method.
462    matches: function(attrs) {
463      return !!_.iteratee(attrs, this)(this.attributes);
464    },
465
466    // Set a hash of model attributes on the object, firing `"change"`. This is
467    // the core primitive operation of a model, updating the data and notifying
468    // anyone who needs to know about the change in state. The heart of the beast.
469    set: function(key, val, options) {
470      if (key == null) return this;
471
472      // Handle both `"key", value` and `{key: value}` -style arguments.
473      var attrs;
474      if (typeof key === 'object') {
475        attrs = key;
476        options = val;
477      } else {
478        (attrs = {})[key] = val;
479      }
480
481      options || (options = {});
482
483      // Run validation.
484      if (!this._validate(attrs, options)) return false;
485
486      // Extract attributes and options.
487      var unset      = options.unset;
488      var silent     = options.silent;
489      var changes    = [];
490      var changing   = this._changing;
491      this._changing = true;
492
493      if (!changing) {
494        this._previousAttributes = _.clone(this.attributes);
495        this.changed = {};
496      }
497
498      var current = this.attributes;
499      var changed = this.changed;
500      var prev    = this._previousAttributes;
501
502      // For each `set` attribute, update or delete the current value.
503      for (var attr in attrs) {
504        val = attrs[attr];
505        if (!_.isEqual(current[attr], val)) changes.push(attr);
506        if (!_.isEqual(prev[attr], val)) {
507          changed[attr] = val;
508        } else {
509          delete changed[attr];
510        }
511        unset ? delete current[attr] : current[attr] = val;
512      }
513
514      // Update the `id`.
515      if (this.idAttribute in attrs) this.id = this.get(this.idAttribute);
516
517      // Trigger all relevant attribute changes.
518      if (!silent) {
519        if (changes.length) this._pending = options;
520        for (var i = 0; i < changes.length; i++) {
521          this.trigger('change:' + changes[i], this, current[changes[i]], options);
522        }
523      }
524
525      // You might be wondering why there's a `while` loop here. Changes can
526      // be recursively nested within `"change"` events.
527      if (changing) return this;
528      if (!silent) {
529        while (this._pending) {
530          options = this._pending;
531          this._pending = false;
532          this.trigger('change', this, options);
533        }
534      }
535      this._pending = false;
536      this._changing = false;
537      return this;
538    },
539
540    // Remove an attribute from the model, firing `"change"`. `unset` is a noop
541    // if the attribute doesn't exist.
542    unset: function(attr, options) {
543      return this.set(attr, void 0, _.extend({}, options, {unset: true}));
544    },
545
546    // Clear all attributes on the model, firing `"change"`.
547    clear: function(options) {
548      var attrs = {};
549      for (var key in this.attributes) attrs[key] = void 0;
550      return this.set(attrs, _.extend({}, options, {unset: true}));
551    },
552
553    // Determine if the model has changed since the last `"change"` event.
554    // If you specify an attribute name, determine if that attribute has changed.
555    hasChanged: function(attr) {
556      if (attr == null) return !_.isEmpty(this.changed);
557      return _.has(this.changed, attr);
558    },
559
560    // Return an object containing all the attributes that have changed, or
561    // false if there are no changed attributes. Useful for determining what
562    // parts of a view need to be updated and/or what attributes need to be
563    // persisted to the server. Unset attributes will be set to undefined.
564    // You can also pass an attributes object to diff against the model,
565    // determining if there *would be* a change.
566    changedAttributes: function(diff) {
567      if (!diff) return this.hasChanged() ? _.clone(this.changed) : false;
568      var old = this._changing ? this._previousAttributes : this.attributes;
569      var changed = {};
570      var hasChanged;
571      for (var attr in diff) {
572        var val = diff[attr];
573        if (_.isEqual(old[attr], val)) continue;
574        changed[attr] = val;
575        hasChanged = true;
576      }
577      return hasChanged ? changed : false;
578    },
579
580    // Get the previous value of an attribute, recorded at the time the last
581    // `"change"` event was fired.
582    previous: function(attr) {
583      if (attr == null || !this._previousAttributes) return null;
584      return this._previousAttributes[attr];
585    },
586
587    // Get all of the attributes of the model at the time of the previous
588    // `"change"` event.
589    previousAttributes: function() {
590      return _.clone(this._previousAttributes);
591    },
592
593    // Fetch the model from the server, merging the response with the model's
594    // local attributes. Any changed attributes will trigger a "change" event.
595    fetch: function(options) {
596      options = _.extend({parse: true}, options);
597      var model = this;
598      var success = options.success;
599      options.success = function(resp) {
600        var serverAttrs = options.parse ? model.parse(resp, options) : resp;
601        if (!model.set(serverAttrs, options)) return false;
602        if (success) success.call(options.context, model, resp, options);
603        model.trigger('sync', model, resp, options);
604      };
605      wrapError(this, options);
606      return this.sync('read', this, options);
607    },
608
609    // Set a hash of model attributes, and sync the model to the server.
610    // If the server returns an attributes hash that differs, the model's
611    // state will be `set` again.
612    save: function(key, val, options) {
613      // Handle both `"key", value` and `{key: value}` -style arguments.
614      var attrs;
615      if (key == null || typeof key === 'object') {
616        attrs = key;
617        options = val;
618      } else {
619        (attrs = {})[key] = val;
620      }
621
622      options = _.extend({validate: true, parse: true}, options);
623      var wait = options.wait;
624
625      // If we're not waiting and attributes exist, save acts as
626      // `set(attr).save(null, opts)` with validation. Otherwise, check if
627      // the model will be valid when the attributes, if any, are set.
628      if (attrs && !wait) {
629        if (!this.set(attrs, options)) return false;
630      } else if (!this._validate(attrs, options)) {
631        return false;
632      }
633
634      // After a successful server-side save, the client is (optionally)
635      // updated with the server-side state.
636      var model = this;
637      var success = options.success;
638      var attributes = this.attributes;
639      options.success = function(resp) {
640        // Ensure attributes are restored during synchronous saves.
641        model.attributes = attributes;
642        var serverAttrs = options.parse ? model.parse(resp, options) : resp;
643        if (wait) serverAttrs = _.extend({}, attrs, serverAttrs);
644        if (serverAttrs && !model.set(serverAttrs, options)) return false;
645        if (success) success.call(options.context, model, resp, options);
646        model.trigger('sync', model, resp, options);
647      };
648      wrapError(this, options);
649
650      // Set temporary attributes if `{wait: true}` to properly find new ids.
651      if (attrs && wait) this.attributes = _.extend({}, attributes, attrs);
652
653      var method = this.isNew() ? 'create' : (options.patch ? 'patch' : 'update');
654      if (method === 'patch' && !options.attrs) options.attrs = attrs;
655      var xhr = this.sync(method, this, options);
656
657      // Restore attributes.
658      this.attributes = attributes;
659
660      return xhr;
661    },
662
663    // Destroy this model on the server if it was already persisted.
664    // Optimistically removes the model from its collection, if it has one.
665    // If `wait: true` is passed, waits for the server to respond before removal.
666    destroy: function(options) {
667      options = options ? _.clone(options) : {};
668      var model = this;
669      var success = options.success;
670      var wait = options.wait;
671
672      var destroy = function() {
673        model.stopListening();
674        model.trigger('destroy', model, model.collection, options);
675      };
676
677      options.success = function(resp) {
678        if (wait) destroy();
679        if (success) success.call(options.context, model, resp, options);
680        if (!model.isNew()) model.trigger('sync', model, resp, options);
681      };
682
683      var xhr = false;
684      if (this.isNew()) {
685        _.defer(options.success);
686      } else {
687        wrapError(this, options);
688        xhr = this.sync('delete', this, options);
689      }
690      if (!wait) destroy();
691      return xhr;
692    },
693
694    // Default URL for the model's representation on the server -- if you're
695    // using Backbone's restful methods, override this to change the endpoint
696    // that will be called.
697    url: function() {
698      var base =
699        _.result(this, 'urlRoot') ||
700        _.result(this.collection, 'url') ||
701        urlError();
702      if (this.isNew()) return base;
703      var id = this.get(this.idAttribute);
704      return base.replace(/[^\/]$/, '$&/') + encodeURIComponent(id);
705    },
706
707    // **parse** converts a response into the hash of attributes to be `set` on
708    // the model. The default implementation is just to pass the response along.
709    parse: function(resp, options) {
710      return resp;
711    },
712
713    // Create a new model with identical attributes to this one.
714    clone: function() {
715      return new this.constructor(this.attributes);
716    },
717
718    // A model is new if it has never been saved to the server, and lacks an id.
719    isNew: function() {
720      return !this.has(this.idAttribute);
721    },
722
723    // Check if the model is currently in a valid state.
724    isValid: function(options) {
725      return this._validate({}, _.extend({}, options, {validate: true}));
726    },
727
728    // Run validation against the next complete set of model attributes,
729    // returning `true` if all is well. Otherwise, fire an `"invalid"` event.
730    _validate: function(attrs, options) {
731      if (!options.validate || !this.validate) return true;
732      attrs = _.extend({}, this.attributes, attrs);
733      var error = this.validationError = this.validate(attrs, options) || null;
734      if (!error) return true;
735      this.trigger('invalid', this, error, _.extend(options, {validationError: error}));
736      return false;
737    }
738
739  });
740
741  // Underscore methods that we want to implement on the Model, mapped to the
742  // number of arguments they take.
743  var modelMethods = {keys: 1, values: 1, pairs: 1, invert: 1, pick: 0,
744      omit: 0, chain: 1, isEmpty: 1};
745
746  // Mix in each Underscore method as a proxy to `Model#attributes`.
747  addUnderscoreMethods(Model, modelMethods, 'attributes');
748
749  // Backbone.Collection
750  // -------------------
751
752  // If models tend to represent a single row of data, a Backbone Collection is
753  // more analogous to a table full of data ... or a small slice or page of that
754  // table, or a collection of rows that belong together for a particular reason
755  // -- all of the messages in this particular folder, all of the documents
756  // belonging to this particular author, and so on. Collections maintain
757  // indexes of their models, both in order, and for lookup by `id`.
758
759  // Create a new **Collection**, perhaps to contain a specific type of `model`.
760  // If a `comparator` is specified, the Collection will maintain
761  // its models in sort order, as they're added and removed.
762  var Collection = Backbone.Collection = function(models, options) {
763    options || (options = {});
764    this.preinitialize.apply(this, arguments);
765    if (options.model) this.model = options.model;
766    if (options.comparator !== void 0) this.comparator = options.comparator;
767    this._reset();
768    this.initialize.apply(this, arguments);
769    if (models) this.reset(models, _.extend({silent: true}, options));
770  };
771
772  // Default options for `Collection#set`.
773  var setOptions = {add: true, remove: true, merge: true};
774  var addOptions = {add: true, remove: false};
775
776  // Splices `insert` into `array` at index `at`.
777  var splice = function(array, insert, at) {
778    at = Math.min(Math.max(at, 0), array.length);
779    var tail = Array(array.length - at);
780    var length = insert.length;
781    var i;
782    for (i = 0; i < tail.length; i++) tail[i] = array[i + at];
783    for (i = 0; i < length; i++) array[i + at] = insert[i];
784    for (i = 0; i < tail.length; i++) array[i + length + at] = tail[i];
785  };
786
787  // Define the Collection's inheritable methods.
788  _.extend(Collection.prototype, Events, {
789
790    // The default model for a collection is just a **Backbone.Model**.
791    // This should be overridden in most cases.
792    model: Model,
793
794
795    // preinitialize is an empty function by default. You can override it with a function
796    // or object.  preinitialize will run before any instantiation logic is run in the Collection.
797    preinitialize: function(){},
798
799    // Initialize is an empty function by default. Override it with your own
800    // initialization logic.
801    initialize: function(){},
802
803    // The JSON representation of a Collection is an array of the
804    // models' attributes.
805    toJSON: function(options) {
806      return this.map(function(model) { return model.toJSON(options); });
807    },
808
809    // Proxy `Backbone.sync` by default.
810    sync: function() {
811      return Backbone.sync.apply(this, arguments);
812    },
813
814    // Add a model, or list of models to the set. `models` may be Backbone
815    // Models or raw JavaScript objects to be converted to Models, or any
816    // combination of the two.
817    add: function(models, options) {
818      return this.set(models, _.extend({merge: false}, options, addOptions));
819    },
820
821    // Remove a model, or a list of models from the set.
822    remove: function(models, options) {
823      options = _.extend({}, options);
824      var singular = !_.isArray(models);
825      models = singular ? [models] : models.slice();
826      var removed = this._removeModels(models, options);
827      if (!options.silent && removed.length) {
828        options.changes = {added: [], merged: [], removed: removed};
829        this.trigger('update', this, options);
830      }
831      return singular ? removed[0] : removed;
832    },
833
834    // Update a collection by `set`-ing a new list of models, adding new ones,
835    // removing models that are no longer present, and merging models that
836    // already exist in the collection, as necessary. Similar to **Model#set**,
837    // the core operation for updating the data contained by the collection.
838    set: function(models, options) {
839      if (models == null) return;
840
841      options = _.extend({}, setOptions, options);
842      if (options.parse && !this._isModel(models)) {
843        models = this.parse(models, options) || [];
844      }
845
846      var singular = !_.isArray(models);
847      models = singular ? [models] : models.slice();
848
849      var at = options.at;
850      if (at != null) at = +at;
851      if (at > this.length) at = this.length;
852      if (at < 0) at += this.length + 1;
853
854      var set = [];
855      var toAdd = [];
856      var toMerge = [];
857      var toRemove = [];
858      var modelMap = {};
859
860      var add = options.add;
861      var merge = options.merge;
862      var remove = options.remove;
863
864      var sort = false;
865      var sortable = this.comparator && at == null && options.sort !== false;
866      var sortAttr = _.isString(this.comparator) ? this.comparator : null;
867
868      // Turn bare objects into model references, and prevent invalid models
869      // from being added.
870      var model, i;
871      for (i = 0; i < models.length; i++) {
872        model = models[i];
873
874        // If a duplicate is found, prevent it from being added and
875        // optionally merge it into the existing model.
876        var existing = this.get(model);
877        if (existing) {
878          if (merge && model !== existing) {
879            var attrs = this._isModel(model) ? model.attributes : model;
880            if (options.parse) attrs = existing.parse(attrs, options);
881            existing.set(attrs, options);
882            toMerge.push(existing);
883            if (sortable && !sort) sort = existing.hasChanged(sortAttr);
884          }
885          if (!modelMap[existing.cid]) {
886            modelMap[existing.cid] = true;
887            set.push(existing);
888          }
889          models[i] = existing;
890
891        // If this is a new, valid model, push it to the `toAdd` list.
892        } else if (add) {
893          model = models[i] = this._prepareModel(model, options);
894          if (model) {
895            toAdd.push(model);
896            this._addReference(model, options);
897            modelMap[model.cid] = true;
898            set.push(model);
899          }
900        }
901      }
902
903      // Remove stale models.
904      if (remove) {
905        for (i = 0; i < this.length; i++) {
906          model = this.models[i];
907          if (!modelMap[model.cid]) toRemove.push(model);
908        }
909        if (toRemove.length) this._removeModels(toRemove, options);
910      }
911
912      // See if sorting is needed, update `length` and splice in new models.
913      var orderChanged = false;
914      var replace = !sortable && add && remove;
915      if (set.length && replace) {
916        orderChanged = this.length !== set.length || _.some(this.models, function(m, index) {
917          return m !== set[index];
918        });
919        this.models.length = 0;
920        splice(this.models, set, 0);
921        this.length = this.models.length;
922      } else if (toAdd.length) {
923        if (sortable) sort = true;
924        splice(this.models, toAdd, at == null ? this.length : at);
925        this.length = this.models.length;
926      }
927
928      // Silently sort the collection if appropriate.
929      if (sort) this.sort({silent: true});
930
931      // Unless silenced, it's time to fire all appropriate add/sort/update events.
932      if (!options.silent) {
933        for (i = 0; i < toAdd.length; i++) {
934          if (at != null) options.index = at + i;
935          model = toAdd[i];
936          model.trigger('add', model, this, options);
937        }
938        if (sort || orderChanged) this.trigger('sort', this, options);
939        if (toAdd.length || toRemove.length || toMerge.length) {
940          options.changes = {
941            added: toAdd,
942            removed: toRemove,
943            merged: toMerge
944          };
945          this.trigger('update', this, options);
946        }
947      }
948
949      // Return the added (or merged) model (or models).
950      return singular ? models[0] : models;
951    },
952
953    // When you have more items than you want to add or remove individually,
954    // you can reset the entire set with a new list of models, without firing
955    // any granular `add` or `remove` events. Fires `reset` when finished.
956    // Useful for bulk operations and optimizations.
957    reset: function(models, options) {
958      options = options ? _.clone(options) : {};
959      for (var i = 0; i < this.models.length; i++) {
960        this._removeReference(this.models[i], options);
961      }
962      options.previousModels = this.models;
963      this._reset();
964      models = this.add(models, _.extend({silent: true}, options));
965      if (!options.silent) this.trigger('reset', this, options);
966      return models;
967    },
968
969    // Add a model to the end of the collection.
970    push: function(model, options) {
971      return this.add(model, _.extend({at: this.length}, options));
972    },
973
974    // Remove a model from the end of the collection.
975    pop: function(options) {
976      var model = this.at(this.length - 1);
977      return this.remove(model, options);
978    },
979
980    // Add a model to the beginning of the collection.
981    unshift: function(model, options) {
982      return this.add(model, _.extend({at: 0}, options));
983    },
984
985    // Remove a model from the beginning of the collection.
986    shift: function(options) {
987      var model = this.at(0);
988      return this.remove(model, options);
989    },
990
991    // Slice out a sub-array of models from the collection.
992    slice: function() {
993      return slice.apply(this.models, arguments);
994    },
995
996    // Get a model from the set by id, cid, model object with id or cid
997    // properties, or an attributes object that is transformed through modelId.
998    get: function(obj) {
999      if (obj == null) return void 0;
1000      return this._byId[obj] ||
1001        this._byId[this.modelId(obj.attributes || obj)] ||
1002        obj.cid && this._byId[obj.cid];
1003    },
1004
1005    // Returns `true` if the model is in the collection.
1006    has: function(obj) {
1007      return this.get(obj) != null;
1008    },
1009
1010    // Get the model at the given index.
1011    at: function(index) {
1012      if (index < 0) index += this.length;
1013      return this.models[index];
1014    },
1015
1016    // Return models with matching attributes. Useful for simple cases of
1017    // `filter`.
1018    where: function(attrs, first) {
1019      return this[first ? 'find' : 'filter'](attrs);
1020    },
1021
1022    // Return the first model with matching attributes. Useful for simple cases
1023    // of `find`.
1024    findWhere: function(attrs) {
1025      return this.where(attrs, true);
1026    },
1027
1028    // Force the collection to re-sort itself. You don't need to call this under
1029    // normal circumstances, as the set will maintain sort order as each item
1030    // is added.
1031    sort: function(options) {
1032      var comparator = this.comparator;
1033      if (!comparator) throw new Error('Cannot sort a set without a comparator');
1034      options || (options = {});
1035
1036      var length = comparator.length;
1037      if (_.isFunction(comparator)) comparator = _.bind(comparator, this);
1038
1039      // Run sort based on type of `comparator`.
1040      if (length === 1 || _.isString(comparator)) {
1041        this.models = this.sortBy(comparator);
1042      } else {
1043        this.models.sort(comparator);
1044      }
1045      if (!options.silent) this.trigger('sort', this, options);
1046      return this;
1047    },
1048
1049    // Pluck an attribute from each model in the collection.
1050    pluck: function(attr) {
1051      return this.map(attr + '');
1052    },
1053
1054    // Fetch the default set of models for this collection, resetting the
1055    // collection when they arrive. If `reset: true` is passed, the response
1056    // data will be passed through the `reset` method instead of `set`.
1057    fetch: function(options) {
1058      options = _.extend({parse: true}, options);
1059      var success = options.success;
1060      var collection = this;
1061      options.success = function(resp) {
1062        var method = options.reset ? 'reset' : 'set';
1063        collection[method](resp, options);
1064        if (success) success.call(options.context, collection, resp, options);
1065        collection.trigger('sync', collection, resp, options);
1066      };
1067      wrapError(this, options);
1068      return this.sync('read', this, options);
1069    },
1070
1071    // Create a new instance of a model in this collection. Add the model to the
1072    // collection immediately, unless `wait: true` is passed, in which case we
1073    // wait for the server to agree.
1074    create: function(model, options) {
1075      options = options ? _.clone(options) : {};
1076      var wait = options.wait;
1077      model = this._prepareModel(model, options);
1078      if (!model) return false;
1079      if (!wait) this.add(model, options);
1080      var collection = this;
1081      var success = options.success;
1082      options.success = function(m, resp, callbackOpts) {
1083        if (wait) collection.add(m, callbackOpts);
1084        if (success) success.call(callbackOpts.context, m, resp, callbackOpts);
1085      };
1086      model.save(null, options);
1087      return model;
1088    },
1089
1090    // **parse** converts a response into a list of models to be added to the
1091    // collection. The default implementation is just to pass it through.
1092    parse: function(resp, options) {
1093      return resp;
1094    },
1095
1096    // Create a new collection with an identical list of models as this one.
1097    clone: function() {
1098      return new this.constructor(this.models, {
1099        model: this.model,
1100        comparator: this.comparator
1101      });
1102    },
1103
1104    // Define how to uniquely identify models in the collection.
1105    modelId: function(attrs) {
1106      return attrs[this.model.prototype.idAttribute || 'id'];
1107    },
1108
1109    // Private method to reset all internal state. Called when the collection
1110    // is first initialized or reset.
1111    _reset: function() {
1112      this.length = 0;
1113      this.models = [];
1114      this._byId  = {};
1115    },
1116
1117    // Prepare a hash of attributes (or other model) to be added to this
1118    // collection.
1119    _prepareModel: function(attrs, options) {
1120      if (this._isModel(attrs)) {
1121        if (!attrs.collection) attrs.collection = this;
1122        return attrs;
1123      }
1124      options = options ? _.clone(options) : {};
1125      options.collection = this;
1126      var model = new this.model(attrs, options);
1127      if (!model.validationError) return model;
1128      this.trigger('invalid', this, model.validationError, options);
1129      return false;
1130    },
1131
1132    // Internal method called by both remove and set.
1133    _removeModels: function(models, options) {
1134      var removed = [];
1135      for (var i = 0; i < models.length; i++) {
1136        var model = this.get(models[i]);
1137        if (!model) continue;
1138
1139        var index = this.indexOf(model);
1140        this.models.splice(index, 1);
1141        this.length--;
1142
1143        // Remove references before triggering 'remove' event to prevent an
1144        // infinite loop. #3693
1145        delete this._byId[model.cid];
1146        var id = this.modelId(model.attributes);
1147        if (id != null) delete this._byId[id];
1148
1149        if (!options.silent) {
1150          options.index = index;
1151          model.trigger('remove', model, this, options);
1152        }
1153
1154        removed.push(model);
1155        this._removeReference(model, options);
1156      }
1157      return removed;
1158    },
1159
1160    // Method for checking whether an object should be considered a model for
1161    // the purposes of adding to the collection.
1162    _isModel: function(model) {
1163      return model instanceof Model;
1164    },
1165
1166    // Internal method to create a model's ties to a collection.
1167    _addReference: function(model, options) {
1168      this._byId[model.cid] = model;
1169      var id = this.modelId(model.attributes);
1170      if (id != null) this._byId[id] = model;
1171      model.on('all', this._onModelEvent, this);
1172    },
1173
1174    // Internal method to sever a model's ties to a collection.
1175    _removeReference: function(model, options) {
1176      delete this._byId[model.cid];
1177      var id = this.modelId(model.attributes);
1178      if (id != null) delete this._byId[id];
1179      if (this === model.collection) delete model.collection;
1180      model.off('all', this._onModelEvent, this);
1181    },
1182
1183    // Internal method called every time a model in the set fires an event.
1184    // Sets need to update their indexes when models change ids. All other
1185    // events simply proxy through. "add" and "remove" events that originate
1186    // in other collections are ignored.
1187    _onModelEvent: function(event, model, collection, options) {
1188      if (model) {
1189        if ((event === 'add' || event === 'remove') && collection !== this) return;
1190        if (event === 'destroy') this.remove(model, options);
1191        if (event === 'change') {
1192          var prevId = this.modelId(model.previousAttributes());
1193          var id = this.modelId(model.attributes);
1194          if (prevId !== id) {
1195            if (prevId != null) delete this._byId[prevId];
1196            if (id != null) this._byId[id] = model;
1197          }
1198        }
1199      }
1200      this.trigger.apply(this, arguments);
1201    }
1202
1203  });
1204
1205  // Underscore methods that we want to implement on the Collection.
1206  // 90% of the core usefulness of Backbone Collections is actually implemented
1207  // right here:
1208  var collectionMethods = {forEach: 3, each: 3, map: 3, collect: 3, reduce: 0,
1209      foldl: 0, inject: 0, reduceRight: 0, foldr: 0, find: 3, detect: 3, filter: 3,
1210      select: 3, reject: 3, every: 3, all: 3, some: 3, any: 3, include: 3, includes: 3,
1211      contains: 3, invoke: 0, max: 3, min: 3, toArray: 1, size: 1, first: 3,
1212      head: 3, take: 3, initial: 3, rest: 3, tail: 3, drop: 3, last: 3,
1213      without: 0, difference: 0, indexOf: 3, shuffle: 1, lastIndexOf: 3,
1214      isEmpty: 1, chain: 1, sample: 3, partition: 3, groupBy: 3, countBy: 3,
1215      sortBy: 3, indexBy: 3, findIndex: 3, findLastIndex: 3};
1216
1217  // Mix in each Underscore method as a proxy to `Collection#models`.
1218  addUnderscoreMethods(Collection, collectionMethods, 'models');
1219
1220  // Backbone.View
1221  // -------------
1222
1223  // Backbone Views are almost more convention than they are actual code. A View
1224  // is simply a JavaScript object that represents a logical chunk of UI in the
1225  // DOM. This might be a single item, an entire list, a sidebar or panel, or
1226  // even the surrounding frame which wraps your whole app. Defining a chunk of
1227  // UI as a **View** allows you to define your DOM events declaratively, without
1228  // having to worry about render order ... and makes it easy for the view to
1229  // react to specific changes in the state of your models.
1230
1231  // Creating a Backbone.View creates its initial element outside of the DOM,
1232  // if an existing element is not provided...
1233  var View = Backbone.View = function(options) {
1234    this.cid = _.uniqueId('view');
1235    this.preinitialize.apply(this, arguments);
1236    _.extend(this, _.pick(options, viewOptions));
1237    this._ensureElement();
1238    this.initialize.apply(this, arguments);
1239  };
1240
1241  // Cached regex to split keys for `delegate`.
1242  var delegateEventSplitter = /^(\S+)\s*(.*)$/;
1243
1244  // List of view options to be set as properties.
1245  var viewOptions = ['model', 'collection', 'el', 'id', 'attributes', 'className', 'tagName', 'events'];
1246
1247  // Set up all inheritable **Backbone.View** properties and methods.
1248  _.extend(View.prototype, Events, {
1249
1250    // The default `tagName` of a View's element is `"div"`.
1251    tagName: 'div',
1252
1253    // jQuery delegate for element lookup, scoped to DOM elements within the
1254    // current view. This should be preferred to global lookups where possible.
1255    $: function(selector) {
1256      return this.$el.find(selector);
1257    },
1258
1259    // preinitialize is an empty function by default. You can override it with a function
1260    // or object.  preinitialize will run before any instantiation logic is run in the View
1261    preinitialize: function(){},
1262
1263    // Initialize is an empty function by default. Override it with your own
1264    // initialization logic.
1265    initialize: function(){},
1266
1267    // **render** is the core function that your view should override, in order
1268    // to populate its element (`this.el`), with the appropriate HTML. The
1269    // convention is for **render** to always return `this`.
1270    render: function() {
1271      return this;
1272    },
1273
1274    // Remove this view by taking the element out of the DOM, and removing any
1275    // applicable Backbone.Events listeners.
1276    remove: function() {
1277      this._removeElement();
1278      this.stopListening();
1279      return this;
1280    },
1281
1282    // Remove this view's element from the document and all event listeners
1283    // attached to it. Exposed for subclasses using an alternative DOM
1284    // manipulation API.
1285    _removeElement: function() {
1286      this.$el.remove();
1287    },
1288
1289    // Change the view's element (`this.el` property) and re-delegate the
1290    // view's events on the new element.
1291    setElement: function(element) {
1292      this.undelegateEvents();
1293      this._setElement(element);
1294      this.delegateEvents();
1295      return this;
1296    },
1297
1298    // Creates the `this.el` and `this.$el` references for this view using the
1299    // given `el`. `el` can be a CSS selector or an HTML string, a jQuery
1300    // context or an element. Subclasses can override this to utilize an
1301    // alternative DOM manipulation API and are only required to set the
1302    // `this.el` property.
1303    _setElement: function(el) {
1304      this.$el = el instanceof Backbone.$ ? el : Backbone.$(el);
1305      this.el = this.$el[0];
1306    },
1307
1308    // Set callbacks, where `this.events` is a hash of
1309    //
1310    // *{"event selector": "callback"}*
1311    //
1312    //     {
1313    //       'mousedown .title':  'edit',
1314    //       'click .button':     'save',
1315    //       'click .open':       function(e) { ... }
1316    //     }
1317    //
1318    // pairs. Callbacks will be bound to the view, with `this` set properly.
1319    // Uses event delegation for efficiency.
1320    // Omitting the selector binds the event to `this.el`.
1321    delegateEvents: function(events) {
1322      events || (events = _.result(this, 'events'));
1323      if (!events) return this;
1324      this.undelegateEvents();
1325      for (var key in events) {
1326        var method = events[key];
1327        if (!_.isFunction(method)) method = this[method];
1328        if (!method) continue;
1329        var match = key.match(delegateEventSplitter);
1330        this.delegate(match[1], match[2], _.bind(method, this));
1331      }
1332      return this;
1333    },
1334
1335    // Add a single event listener to the view's element (or a child element
1336    // using `selector`). This only works for delegate-able events: not `focus`,
1337    // `blur`, and not `change`, `submit`, and `reset` in Internet Explorer.
1338    delegate: function(eventName, selector, listener) {
1339      this.$el.on(eventName + '.delegateEvents' + this.cid, selector, listener);
1340      return this;
1341    },
1342
1343    // Clears all callbacks previously bound to the view by `delegateEvents`.
1344    // You usually don't need to use this, but may wish to if you have multiple
1345    // Backbone views attached to the same DOM element.
1346    undelegateEvents: function() {
1347      if (this.$el) this.$el.off('.delegateEvents' + this.cid);
1348      return this;
1349    },
1350
1351    // A finer-grained `undelegateEvents` for removing a single delegated event.
1352    // `selector` and `listener` are both optional.
1353    undelegate: function(eventName, selector, listener) {
1354      this.$el.off(eventName + '.delegateEvents' + this.cid, selector, listener);
1355      return this;
1356    },
1357
1358    // Produces a DOM element to be assigned to your view. Exposed for
1359    // subclasses using an alternative DOM manipulation API.
1360    _createElement: function(tagName) {
1361      return document.createElement(tagName);
1362    },
1363
1364    // Ensure that the View has a DOM element to render into.
1365    // If `this.el` is a string, pass it through `$()`, take the first
1366    // matching element, and re-assign it to `el`. Otherwise, create
1367    // an element from the `id`, `className` and `tagName` properties.
1368    _ensureElement: function() {
1369      if (!this.el) {
1370        var attrs = _.extend({}, _.result(this, 'attributes'));
1371        if (this.id) attrs.id = _.result(this, 'id');
1372        if (this.className) attrs['class'] = _.result(this, 'className');
1373        this.setElement(this._createElement(_.result(this, 'tagName')));
1374        this._setAttributes(attrs);
1375      } else {
1376        this.setElement(_.result(this, 'el'));
1377      }
1378    },
1379
1380    // Set attributes from a hash on this view's element.  Exposed for
1381    // subclasses using an alternative DOM manipulation API.
1382    _setAttributes: function(attributes) {
1383      this.$el.attr(attributes);
1384    }
1385
1386  });
1387
1388  // Backbone.sync
1389  // -------------
1390
1391  // Override this function to change the manner in which Backbone persists
1392  // models to the server. You will be passed the type of request, and the
1393  // model in question. By default, makes a RESTful Ajax request
1394  // to the model's `url()`. Some possible customizations could be:
1395  //
1396  // * Use `setTimeout` to batch rapid-fire updates into a single request.
1397  // * Send up the models as XML instead of JSON.
1398  // * Persist models via WebSockets instead of Ajax.
1399  //
1400  // Turn on `Backbone.emulateHTTP` in order to send `PUT` and `DELETE` requests
1401  // as `POST`, with a `_method` parameter containing the true HTTP method,
1402  // as well as all requests with the body as `application/x-www-form-urlencoded`
1403  // instead of `application/json` with the model in a param named `model`.
1404  // Useful when interfacing with server-side languages like **PHP** that make
1405  // it difficult to read the body of `PUT` requests.
1406  Backbone.sync = function(method, model, options) {
1407    var type = methodMap[method];
1408
1409    // Default options, unless specified.
1410    _.defaults(options || (options = {}), {
1411      emulateHTTP: Backbone.emulateHTTP,
1412      emulateJSON: Backbone.emulateJSON
1413    });
1414
1415    // Default JSON-request options.
1416    var params = {type: type, dataType: 'json'};
1417
1418    // Ensure that we have a URL.
1419    if (!options.url) {
1420      params.url = _.result(model, 'url') || urlError();
1421    }
1422
1423    // Ensure that we have the appropriate request data.
1424    if (options.data == null && model && (method === 'create' || method === 'update' || method === 'patch')) {
1425      params.contentType = 'application/json';
1426      params.data = JSON.stringify(options.attrs || model.toJSON(options));
1427    }
1428
1429    // For older servers, emulate JSON by encoding the request into an HTML-form.
1430    if (options.emulateJSON) {
1431      params.contentType = 'application/x-www-form-urlencoded';
1432      params.data = params.data ? {model: params.data} : {};
1433    }
1434
1435    // For older servers, emulate HTTP by mimicking the HTTP method with `_method`
1436    // And an `X-HTTP-Method-Override` header.
1437    if (options.emulateHTTP && (type === 'PUT' || type === 'DELETE' || type === 'PATCH')) {
1438      params.type = 'POST';
1439      if (options.emulateJSON) params.data._method = type;
1440      var beforeSend = options.beforeSend;
1441      options.beforeSend = function(xhr) {
1442        xhr.setRequestHeader('X-HTTP-Method-Override', type);
1443        if (beforeSend) return beforeSend.apply(this, arguments);
1444      };
1445    }
1446
1447    // Don't process data on a non-GET request.
1448    if (params.type !== 'GET' && !options.emulateJSON) {
1449      params.processData = false;
1450    }
1451
1452    // Pass along `textStatus` and `errorThrown` from jQuery.
1453    var error = options.error;
1454    options.error = function(xhr, textStatus, errorThrown) {
1455      options.textStatus = textStatus;
1456      options.errorThrown = errorThrown;
1457      if (error) error.call(options.context, xhr, textStatus, errorThrown);
1458    };
1459
1460    // Make the request, allowing the user to override any Ajax options.
1461    var xhr = options.xhr = Backbone.ajax(_.extend(params, options));
1462    model.trigger('request', model, xhr, options);
1463    return xhr;
1464  };
1465
1466  // Map from CRUD to HTTP for our default `Backbone.sync` implementation.
1467  var methodMap = {
1468    'create': 'POST',
1469    'update': 'PUT',
1470    'patch': 'PATCH',
1471    'delete': 'DELETE',
1472    'read': 'GET'
1473  };
1474
1475  // Set the default implementation of `Backbone.ajax` to proxy through to `$`.
1476  // Override this if you'd like to use a different library.
1477  Backbone.ajax = function() {
1478    return Backbone.$.ajax.apply(Backbone.$, arguments);
1479  };
1480
1481  // Backbone.Router
1482  // ---------------
1483
1484  // Routers map faux-URLs to actions, and fire events when routes are
1485  // matched. Creating a new one sets its `routes` hash, if not set statically.
1486  var Router = Backbone.Router = function(options) {
1487    options || (options = {});
1488    this.preinitialize.apply(this, arguments);
1489    if (options.routes) this.routes = options.routes;
1490    this._bindRoutes();
1491    this.initialize.apply(this, arguments);
1492  };
1493
1494  // Cached regular expressions for matching named param parts and splatted
1495  // parts of route strings.
1496  var optionalParam = /\((.*?)\)/g;
1497  var namedParam    = /(\(\?)?:\w+/g;
1498  var splatParam    = /\*\w+/g;
1499  var escapeRegExp  = /[\-{}\[\]+?.,\\\^$|#\s]/g;
1500
1501  // Set up all inheritable **Backbone.Router** properties and methods.
1502  _.extend(Router.prototype, Events, {
1503
1504    // preinitialize is an empty function by default. You can override it with a function
1505    // or object.  preinitialize will run before any instantiation logic is run in the Router.
1506    preinitialize: function(){},
1507
1508    // Initialize is an empty function by default. Override it with your own
1509    // initialization logic.
1510    initialize: function(){},
1511
1512    // Manually bind a single named route to a callback. For example:
1513    //
1514    //     this.route('search/:query/p:num', 'search', function(query, num) {
1515    //       ...
1516    //     });
1517    //
1518    route: function(route, name, callback) {
1519      if (!_.isRegExp(route)) route = this._routeToRegExp(route);
1520      if (_.isFunction(name)) {
1521        callback = name;
1522        name = '';
1523      }
1524      if (!callback) callback = this[name];
1525      var router = this;
1526      Backbone.history.route(route, function(fragment) {
1527        var args = router._extractParameters(route, fragment);
1528        if (router.execute(callback, args, name) !== false) {
1529          router.trigger.apply(router, ['route:' + name].concat(args));
1530          router.trigger('route', name, args);
1531          Backbone.history.trigger('route', router, name, args);
1532        }
1533      });
1534      return this;
1535    },
1536
1537    // Execute a route handler with the provided parameters.  This is an
1538    // excellent place to do pre-route setup or post-route cleanup.
1539    execute: function(callback, args, name) {
1540      if (callback) callback.apply(this, args);
1541    },
1542
1543    // Simple proxy to `Backbone.history` to save a fragment into the history.
1544    navigate: function(fragment, options) {
1545      Backbone.history.navigate(fragment, options);
1546      return this;
1547    },
1548
1549    // Bind all defined routes to `Backbone.history`. We have to reverse the
1550    // order of the routes here to support behavior where the most general
1551    // routes can be defined at the bottom of the route map.
1552    _bindRoutes: function() {
1553      if (!this.routes) return;
1554      this.routes = _.result(this, 'routes');
1555      var route, routes = _.keys(this.routes);
1556      while ((route = routes.pop()) != null) {
1557        this.route(route, this.routes[route]);
1558      }
1559    },
1560
1561    // Convert a route string into a regular expression, suitable for matching
1562    // against the current location hash.
1563    _routeToRegExp: function(route) {
1564      route = route.replace(escapeRegExp, '\\$&')
1565                   .replace(optionalParam, '(?:$1)?')
1566                   .replace(namedParam, function(match, optional) {
1567                     return optional ? match : '([^/?]+)';
1568                   })
1569                   .replace(splatParam, '([^?]*?)');
1570      return new RegExp('^' + route + '(?:\\?([\\s\\S]*))?$');
1571    },
1572
1573    // Given a route, and a URL fragment that it matches, return the array of
1574    // extracted decoded parameters. Empty or unmatched parameters will be
1575    // treated as `null` to normalize cross-browser behavior.
1576    _extractParameters: function(route, fragment) {
1577      var params = route.exec(fragment).slice(1);
1578      return _.map(params, function(param, i) {
1579        // Don't decode the search params.
1580        if (i === params.length - 1) return param || null;
1581        return param ? decodeURIComponent(param) : null;
1582      });
1583    }
1584
1585  });
1586
1587  // Backbone.History
1588  // ----------------
1589
1590  // Handles cross-browser history management, based on either
1591  // [pushState](http://diveintohtml5.info/history.html) and real URLs, or
1592  // [onhashchange](https://developer.mozilla.org/en-US/docs/DOM/window.onhashchange)
1593  // and URL fragments. If the browser supports neither (old IE, natch),
1594  // falls back to polling.
1595  var History = Backbone.History = function() {
1596    this.handlers = [];
1597    this.checkUrl = _.bind(this.checkUrl, this);
1598
1599    // Ensure that `History` can be used outside of the browser.
1600    if (typeof window !== 'undefined') {
1601      this.location = window.location;
1602      this.history = window.history;
1603    }
1604  };
1605
1606  // Cached regex for stripping a leading hash/slash and trailing space.
1607  var routeStripper = /^[#\/]|\s+$/g;
1608
1609  // Cached regex for stripping leading and trailing slashes.
1610  var rootStripper = /^\/+|\/+$/g;
1611
1612  // Cached regex for stripping urls of hash.
1613  var pathStripper = /#.*$/;
1614
1615  // Has the history handling already been started?
1616  History.started = false;
1617
1618  // Set up all inheritable **Backbone.History** properties and methods.
1619  _.extend(History.prototype, Events, {
1620
1621    // The default interval to poll for hash changes, if necessary, is
1622    // twenty times a second.
1623    interval: 50,
1624
1625    // Are we at the app root?
1626    atRoot: function() {
1627      var path = this.location.pathname.replace(/[^\/]$/, '$&/');
1628      return path === this.root && !this.getSearch();
1629    },
1630
1631    // Does the pathname match the root?
1632    matchRoot: function() {
1633      var path = this.decodeFragment(this.location.pathname);
1634      var rootPath = path.slice(0, this.root.length - 1) + '/';
1635      return rootPath === this.root;
1636    },
1637
1638    // Unicode characters in `location.pathname` are percent encoded so they're
1639    // decoded for comparison. `%25` should not be decoded since it may be part
1640    // of an encoded parameter.
1641    decodeFragment: function(fragment) {
1642      return decodeURI(fragment.replace(/%25/g, '%2525'));
1643    },
1644
1645    // In IE6, the hash fragment and search params are incorrect if the
1646    // fragment contains `?`.
1647    getSearch: function() {
1648      var match = this.location.href.replace(/#.*/, '').match(/\?.+/);
1649      return match ? match[0] : '';
1650    },
1651
1652    // Gets the true hash value. Cannot use location.hash directly due to bug
1653    // in Firefox where location.hash will always be decoded.
1654    getHash: function(window) {
1655      var match = (window || this).location.href.match(/#(.*)$/);
1656      return match ? match[1] : '';
1657    },
1658
1659    // Get the pathname and search params, without the root.
1660    getPath: function() {
1661      var path = this.decodeFragment(
1662        this.location.pathname + this.getSearch()
1663      ).slice(this.root.length - 1);
1664      return path.charAt(0) === '/' ? path.slice(1) : path;
1665    },
1666
1667    // Get the cross-browser normalized URL fragment from the path or hash.
1668    getFragment: function(fragment) {
1669      if (fragment == null) {
1670        if (this._usePushState || !this._wantsHashChange) {
1671          fragment = this.getPath();
1672        } else {
1673          fragment = this.getHash();
1674        }
1675      }
1676      return fragment.replace(routeStripper, '');
1677    },
1678
1679    // Start the hash change handling, returning `true` if the current URL matches
1680    // an existing route, and `false` otherwise.
1681    start: function(options) {
1682      if (History.started) throw new Error('Backbone.history has already been started');
1683      History.started = true;
1684
1685      // Figure out the initial configuration. Do we need an iframe?
1686      // Is pushState desired ... is it available?
1687      this.options          = _.extend({root: '/'}, this.options, options);
1688      this.root             = this.options.root;
1689      this._wantsHashChange = this.options.hashChange !== false;
1690      this._hasHashChange   = 'onhashchange' in window && (document.documentMode === void 0 || document.documentMode > 7);
1691      this._useHashChange   = this._wantsHashChange && this._hasHashChange;
1692      this._wantsPushState  = !!this.options.pushState;
1693      this._hasPushState    = !!(this.history && this.history.pushState);
1694      this._usePushState    = this._wantsPushState && this._hasPushState;
1695      this.fragment         = this.getFragment();
1696
1697      // Normalize root to always include a leading and trailing slash.
1698      this.root = ('/' + this.root + '/').replace(rootStripper, '/');
1699
1700      // Transition from hashChange to pushState or vice versa if both are
1701      // requested.
1702      if (this._wantsHashChange && this._wantsPushState) {
1703
1704        // If we've started off with a route from a `pushState`-enabled
1705        // browser, but we're currently in a browser that doesn't support it...
1706        if (!this._hasPushState && !this.atRoot()) {
1707          var rootPath = this.root.slice(0, -1) || '/';
1708          this.location.replace(rootPath + '#' + this.getPath());
1709          // Return immediately as browser will do redirect to new url
1710          return true;
1711
1712        // Or if we've started out with a hash-based route, but we're currently
1713        // in a browser where it could be `pushState`-based instead...
1714        } else if (this._hasPushState && this.atRoot()) {
1715          this.navigate(this.getHash(), {replace: true});
1716        }
1717
1718      }
1719
1720      // Proxy an iframe to handle location events if the browser doesn't
1721      // support the `hashchange` event, HTML5 history, or the user wants
1722      // `hashChange` but not `pushState`.
1723      if (!this._hasHashChange && this._wantsHashChange && !this._usePushState) {
1724        this.iframe = document.createElement('iframe');
1725        this.iframe.src = 'javascript:0';
1726        this.iframe.style.display = 'none';
1727        this.iframe.tabIndex = -1;
1728        var body = document.body;
1729        // Using `appendChild` will throw on IE < 9 if the document is not ready.
1730        var iWindow = body.insertBefore(this.iframe, body.firstChild).contentWindow;
1731        iWindow.document.open();
1732        iWindow.document.close();
1733        iWindow.location.hash = '#' + this.fragment;
1734      }
1735
1736      // Add a cross-platform `addEventListener` shim for older browsers.
1737      var addEventListener = window.addEventListener || function(eventName, listener) {
1738        return attachEvent('on' + eventName, listener);
1739      };
1740
1741      // Depending on whether we're using pushState or hashes, and whether
1742      // 'onhashchange' is supported, determine how we check the URL state.
1743      if (this._usePushState) {
1744        addEventListener('popstate', this.checkUrl, false);
1745      } else if (this._useHashChange && !this.iframe) {
1746        addEventListener('hashchange', this.checkUrl, false);
1747      } else if (this._wantsHashChange) {
1748        this._checkUrlInterval = setInterval(this.checkUrl, this.interval);
1749      }
1750
1751      if (!this.options.silent) return this.loadUrl();
1752    },
1753
1754    // Disable Backbone.history, perhaps temporarily. Not useful in a real app,
1755    // but possibly useful for unit testing Routers.
1756    stop: function() {
1757      // Add a cross-platform `removeEventListener` shim for older browsers.
1758      var removeEventListener = window.removeEventListener || function(eventName, listener) {
1759        return detachEvent('on' + eventName, listener);
1760      };
1761
1762      // Remove window listeners.
1763      if (this._usePushState) {
1764        removeEventListener('popstate', this.checkUrl, false);
1765      } else if (this._useHashChange && !this.iframe) {
1766        removeEventListener('hashchange', this.checkUrl, false);
1767      }
1768
1769      // Clean up the iframe if necessary.
1770      if (this.iframe) {
1771        document.body.removeChild(this.iframe);
1772        this.iframe = null;
1773      }
1774
1775      // Some environments will throw when clearing an undefined interval.
1776      if (this._checkUrlInterval) clearInterval(this._checkUrlInterval);
1777      History.started = false;
1778    },
1779
1780    // Add a route to be tested when the fragment changes. Routes added later
1781    // may override previous routes.
1782    route: function(route, callback) {
1783      this.handlers.unshift({route: route, callback: callback});
1784    },
1785
1786    // Checks the current URL to see if it has changed, and if it has,
1787    // calls `loadUrl`, normalizing across the hidden iframe.
1788    checkUrl: function(e) {
1789      var current = this.getFragment();
1790
1791      // If the user pressed the back button, the iframe's hash will have
1792      // changed and we should use that for comparison.
1793      if (current === this.fragment && this.iframe) {
1794        current = this.getHash(this.iframe.contentWindow);
1795      }
1796
1797      if (current === this.fragment) return false;
1798      if (this.iframe) this.navigate(current);
1799      this.loadUrl();
1800    },
1801
1802    // Attempt to load the current URL fragment. If a route succeeds with a
1803    // match, returns `true`. If no defined routes matches the fragment,
1804    // returns `false`.
1805    loadUrl: function(fragment) {
1806      // If the root doesn't match, no routes can match either.
1807      if (!this.matchRoot()) return false;
1808      fragment = this.fragment = this.getFragment(fragment);
1809      return _.some(this.handlers, function(handler) {
1810        if (handler.route.test(fragment)) {
1811          handler.callback(fragment);
1812          return true;
1813        }
1814      });
1815    },
1816
1817    // Save a fragment into the hash history, or replace the URL state if the
1818    // 'replace' option is passed. You are responsible for properly URL-encoding
1819    // the fragment in advance.
1820    //
1821    // The options object can contain `trigger: true` if you wish to have the
1822    // route callback be fired (not usually desirable), or `replace: true`, if
1823    // you wish to modify the current URL without adding an entry to the history.
1824    navigate: function(fragment, options) {
1825      if (!History.started) return false;
1826      if (!options || options === true) options = {trigger: !!options};
1827
1828      // Normalize the fragment.
1829      fragment = this.getFragment(fragment || '');
1830
1831      // Don't include a trailing slash on the root.
1832      var rootPath = this.root;
1833      if (fragment === '' || fragment.charAt(0) === '?') {
1834        rootPath = rootPath.slice(0, -1) || '/';
1835      }
1836      var url = rootPath + fragment;
1837
1838      // Strip the fragment of the query and hash for matching.
1839      fragment = fragment.replace(pathStripper, '');
1840
1841      // Decode for matching.
1842      var decodedFragment = this.decodeFragment(fragment);
1843
1844      if (this.fragment === decodedFragment) return;
1845      this.fragment = decodedFragment;
1846
1847      // If pushState is available, we use it to set the fragment as a real URL.
1848      if (this._usePushState) {
1849        this.history[options.replace ? 'replaceState' : 'pushState']({}, document.title, url);
1850
1851      // If hash changes haven't been explicitly disabled, update the hash
1852      // fragment to store history.
1853      } else if (this._wantsHashChange) {
1854        this._updateHash(this.location, fragment, options.replace);
1855        if (this.iframe && fragment !== this.getHash(this.iframe.contentWindow)) {
1856          var iWindow = this.iframe.contentWindow;
1857
1858          // Opening and closing the iframe tricks IE7 and earlier to push a
1859          // history entry on hash-tag change.  When replace is true, we don't
1860          // want this.
1861          if (!options.replace) {
1862            iWindow.document.open();
1863            iWindow.document.close();
1864          }
1865
1866          this._updateHash(iWindow.location, fragment, options.replace);
1867        }
1868
1869      // If you've told us that you explicitly don't want fallback hashchange-
1870      // based history, then `navigate` becomes a page refresh.
1871      } else {
1872        return this.location.assign(url);
1873      }
1874      if (options.trigger) return this.loadUrl(fragment);
1875    },
1876
1877    // Update the hash location, either replacing the current entry, or adding
1878    // a new one to the browser history.
1879    _updateHash: function(location, fragment, replace) {
1880      if (replace) {
1881        var href = location.href.replace(/(javascript:|#).*$/, '');
1882        location.replace(href + '#' + fragment);
1883      } else {
1884        // Some browsers require that `hash` contains a leading #.
1885        location.hash = '#' + fragment;
1886      }
1887    }
1888
1889  });
1890
1891  // Create the default Backbone.history.
1892  Backbone.history = new History;
1893
1894  // Helpers
1895  // -------
1896
1897  // Helper function to correctly set up the prototype chain for subclasses.
1898  // Similar to `goog.inherits`, but uses a hash of prototype properties and
1899  // class properties to be extended.
1900  var extend = function(protoProps, staticProps) {
1901    var parent = this;
1902    var child;
1903
1904    // The constructor function for the new subclass is either defined by you
1905    // (the "constructor" property in your `extend` definition), or defaulted
1906    // by us to simply call the parent constructor.
1907    if (protoProps && _.has(protoProps, 'constructor')) {
1908      child = protoProps.constructor;
1909    } else {
1910      child = function(){ return parent.apply(this, arguments); };
1911    }
1912
1913    // Add static properties to the constructor function, if supplied.
1914    _.extend(child, parent, staticProps);
1915
1916    // Set the prototype chain to inherit from `parent`, without calling
1917    // `parent`'s constructor function and add the prototype properties.
1918    child.prototype = _.create(parent.prototype, protoProps);
1919    child.prototype.constructor = child;
1920
1921    // Set a convenience property in case the parent's prototype is needed
1922    // later.
1923    child.__super__ = parent.prototype;
1924
1925    return child;
1926  };
1927
1928  // Set up inheritance for the model, collection, router, view and history.
1929  Model.extend = Collection.extend = Router.extend = View.extend = History.extend = extend;
1930
1931  // Throw an error when a URL is needed, and none is supplied.
1932  var urlError = function() {
1933    throw new Error('A "url" property or function must be specified');
1934  };
1935
1936  // Wrap an optional error callback with a fallback error event.
1937  var wrapError = function(model, options) {
1938    var error = options.error;
1939    options.error = function(resp) {
1940      if (error) error.call(options.context, model, resp, options);
1941      model.trigger('error', model, resp, options);
1942    };
1943  };
1944
1945  return Backbone;
1946});
1947