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   1  //     Backbone.js 1.6.1
   2  
   3  //     (c) 2010-2024 Jeremy Ashkenas and DocumentCloud
   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, _, $) {
  35  
  36    // Initial Setup
  37    // -------------
  38  
  39    // Save the previous value of the `Backbone` variable, so that it can be
  40    // restored later on, if `noConflict` is used.
  41    var previousBackbone = root.Backbone;
  42  
  43    // Create a local reference to a common array method we'll want to use later.
  44    var slice = Array.prototype.slice;
  45  
  46    // Current version of the library. Keep in sync with `package.json`.
  47    Backbone.VERSION = '1.6.1';
  48  
  49    // For Backbone's purposes, jQuery, Zepto, Ender, or My Library (kidding) owns
  50    // the `$` 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    // Backbone.Events
  72    // ---------------
  73  
  74    // A module that can be mixed in to *any object* in order to provide it with
  75    // a custom event channel. You may bind a callback to an event with `on` or
  76    // remove with `off`; `trigger`-ing an event fires all callbacks in
  77    // succession.
  78    //
  79    //     var object = {};
  80    //     _.extend(object, Backbone.Events);
  81    //     object.on('expand', function(){ alert('expanded'); });
  82    //     object.trigger('expand');
  83    //
  84    var Events = Backbone.Events = {};
  85  
  86    // Regular expression used to split event strings.
  87    var eventSplitter = /\s+/;
  88  
  89    // A private global variable to share between listeners and listenees.
  90    var _listening;
  91  
  92    // Iterates over the standard `event, callback` (as well as the fancy multiple
  93    // space-separated events `"change blur", callback` and jQuery-style event
  94    // maps `{event: callback}`).
  95    var eventsApi = function(iteratee, events, name, callback, opts) {
  96      var i = 0, names;
  97      if (name && typeof name === 'object') {
  98        // Handle event maps.
  99        if (callback !== void 0 && 'context' in opts && opts.context === void 0) opts.context = callback;
 100        for (names = _.keys(name); i < names.length ; i++) {
 101          events = eventsApi(iteratee, events, names[i], name[names[i]], opts);
 102        }
 103      } else if (name && eventSplitter.test(name)) {
 104        // Handle space-separated event names by delegating them individually.
 105        for (names = name.split(eventSplitter); i < names.length; i++) {
 106          events = iteratee(events, names[i], callback, opts);
 107        }
 108      } else {
 109        // Finally, standard events.
 110        events = iteratee(events, name, callback, opts);
 111      }
 112      return events;
 113    };
 114  
 115    // Bind an event to a `callback` function. Passing `"all"` will bind
 116    // the callback to all events fired.
 117    Events.on = function(name, callback, context) {
 118      this._events = eventsApi(onApi, this._events || {}, name, callback, {
 119        context: context,
 120        ctx: this,
 121        listening: _listening
 122      });
 123  
 124      if (_listening) {
 125        var listeners = this._listeners || (this._listeners = {});
 126        listeners[_listening.id] = _listening;
 127        // Allow the listening to use a counter, instead of tracking
 128        // callbacks for library interop
 129        _listening.interop = false;
 130      }
 131  
 132      return this;
 133    };
 134  
 135    // Inversion-of-control versions of `on`. Tell *this* object to listen to
 136    // an event in another object... keeping track of what it's listening to
 137    // for easier unbinding later.
 138    Events.listenTo = function(obj, name, callback) {
 139      if (!obj) return this;
 140      var id = obj._listenId || (obj._listenId = _.uniqueId('l'));
 141      var listeningTo = this._listeningTo || (this._listeningTo = {});
 142      var listening = _listening = listeningTo[id];
 143  
 144      // This object is not listening to any other events on `obj` yet.
 145      // Setup the necessary references to track the listening callbacks.
 146      if (!listening) {
 147        this._listenId || (this._listenId = _.uniqueId('l'));
 148        listening = _listening = listeningTo[id] = new Listening(this, obj);
 149      }
 150  
 151      // Bind callbacks on obj.
 152      var error = tryCatchOn(obj, name, callback, this);
 153      _listening = void 0;
 154  
 155      if (error) throw error;
 156      // If the target obj is not Backbone.Events, track events manually.
 157      if (listening.interop) listening.on(name, callback);
 158  
 159      return this;
 160    };
 161  
 162    // The reducing API that adds a callback to the `events` object.
 163    var onApi = function(events, name, callback, options) {
 164      if (callback) {
 165        var handlers = events[name] || (events[name] = []);
 166        var context = options.context, ctx = options.ctx, listening = options.listening;
 167        if (listening) listening.count++;
 168  
 169        handlers.push({callback: callback, context: context, ctx: context || ctx, listening: listening});
 170      }
 171      return events;
 172    };
 173  
 174    // An try-catch guarded #on function, to prevent poisoning the global
 175    // `_listening` variable.
 176    var tryCatchOn = function(obj, name, callback, context) {
 177      try {
 178        obj.on(name, callback, context);
 179      } catch (e) {
 180        return e;
 181      }
 182    };
 183  
 184    // Remove one or many callbacks. If `context` is null, removes all
 185    // callbacks with that function. If `callback` is null, removes all
 186    // callbacks for the event. If `name` is null, removes all bound
 187    // callbacks for all events.
 188    Events.off = function(name, callback, context) {
 189      if (!this._events) return this;
 190      this._events = eventsApi(offApi, this._events, name, callback, {
 191        context: context,
 192        listeners: this._listeners
 193      });
 194  
 195      return this;
 196    };
 197  
 198    // Tell this object to stop listening to either specific events ... or
 199    // to every object it's currently listening to.
 200    Events.stopListening = function(obj, name, callback) {
 201      var listeningTo = this._listeningTo;
 202      if (!listeningTo) return this;
 203  
 204      var ids = obj ? [obj._listenId] : _.keys(listeningTo);
 205      for (var i = 0; i < ids.length; i++) {
 206        var listening = listeningTo[ids[i]];
 207  
 208        // If listening doesn't exist, this object is not currently
 209        // listening to obj. Break out early.
 210        if (!listening) break;
 211  
 212        listening.obj.off(name, callback, this);
 213        if (listening.interop) listening.off(name, callback);
 214      }
 215      if (_.isEmpty(listeningTo)) this._listeningTo = void 0;
 216  
 217      return this;
 218    };
 219  
 220    // The reducing API that removes a callback from the `events` object.
 221    var offApi = function(events, name, callback, options) {
 222      if (!events) return;
 223  
 224      var context = options.context, listeners = options.listeners;
 225      var i = 0, names;
 226  
 227      // Delete all event listeners and "drop" events.
 228      if (!name && !context && !callback) {
 229        for (names = _.keys(listeners); i < names.length; i++) {
 230          listeners[names[i]].cleanup();
 231        }
 232        return;
 233      }
 234  
 235      names = name ? [name] : _.keys(events);
 236      for (; i < names.length; i++) {
 237        name = names[i];
 238        var handlers = events[name];
 239  
 240        // Bail out if there are no events stored.
 241        if (!handlers) break;
 242  
 243        // Find any remaining events.
 244        var remaining = [];
 245        for (var j = 0; j < handlers.length; j++) {
 246          var handler = handlers[j];
 247          if (
 248            callback && callback !== handler.callback &&
 249              callback !== handler.callback._callback ||
 250                context && context !== handler.context
 251          ) {
 252            remaining.push(handler);
 253          } else {
 254            var listening = handler.listening;
 255            if (listening) listening.off(name, callback);
 256          }
 257        }
 258  
 259        // Replace events if there are any remaining.  Otherwise, clean up.
 260        if (remaining.length) {
 261          events[name] = remaining;
 262        } else {
 263          delete events[name];
 264        }
 265      }
 266  
 267      return events;
 268    };
 269  
 270    // Bind an event to only be triggered a single time. After the first time
 271    // the callback is invoked, its listener will be removed. If multiple events
 272    // are passed in using the space-separated syntax, the handler will fire
 273    // once for each event, not once for a combination of all events.
 274    Events.once = function(name, callback, context) {
 275      // Map the event into a `{event: once}` object.
 276      var events = eventsApi(onceMap, {}, name, callback, this.off.bind(this));
 277      if (typeof name === 'string' && context == null) callback = void 0;
 278      return this.on(events, callback, context);
 279    };
 280  
 281    // Inversion-of-control versions of `once`.
 282    Events.listenToOnce = function(obj, name, callback) {
 283      // Map the event into a `{event: once}` object.
 284      var events = eventsApi(onceMap, {}, name, callback, this.stopListening.bind(this, obj));
 285      return this.listenTo(obj, events);
 286    };
 287  
 288    // Reduces the event callbacks into a map of `{event: onceWrapper}`.
 289    // `offer` unbinds the `onceWrapper` after it has been called.
 290    var onceMap = function(map, name, callback, offer) {
 291      if (callback) {
 292        var once = map[name] = _.once(function() {
 293          offer(name, once);
 294          callback.apply(this, arguments);
 295        });
 296        once._callback = callback;
 297      }
 298      return map;
 299    };
 300  
 301    // Trigger one or many events, firing all bound callbacks. Callbacks are
 302    // passed the same arguments as `trigger` is, apart from the event name
 303    // (unless you're listening on `"all"`, which will cause your callback to
 304    // receive the true name of the event as the first argument).
 305    Events.trigger = function(name) {
 306      if (!this._events) return this;
 307  
 308      var length = Math.max(0, arguments.length - 1);
 309      var args = Array(length);
 310      for (var i = 0; i < length; i++) args[i] = arguments[i + 1];
 311  
 312      eventsApi(triggerApi, this._events, name, void 0, args);
 313      return this;
 314    };
 315  
 316    // Handles triggering the appropriate event callbacks.
 317    var triggerApi = function(objEvents, name, callback, args) {
 318      if (objEvents) {
 319        var events = objEvents[name];
 320        var allEvents = objEvents.all;
 321        if (events && allEvents) allEvents = allEvents.slice();
 322        if (events) triggerEvents(events, args);
 323        if (allEvents) triggerEvents(allEvents, [name].concat(args));
 324      }
 325      return objEvents;
 326    };
 327  
 328    // A difficult-to-believe, but optimized internal dispatch function for
 329    // triggering events. Tries to keep the usual cases speedy (most internal
 330    // Backbone events have 3 arguments).
 331    var triggerEvents = function(events, args) {
 332      var ev, i = -1, l = events.length, a1 = args[0], a2 = args[1], a3 = args[2];
 333      switch (args.length) {
 334        case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx); return;
 335        case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1); return;
 336        case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2); return;
 337        case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2, a3); return;
 338        default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args); return;
 339      }
 340    };
 341  
 342    // A listening class that tracks and cleans up memory bindings
 343    // when all callbacks have been offed.
 344    var Listening = function(listener, obj) {
 345      this.id = listener._listenId;
 346      this.listener = listener;
 347      this.obj = obj;
 348      this.interop = true;
 349      this.count = 0;
 350      this._events = void 0;
 351    };
 352  
 353    Listening.prototype.on = Events.on;
 354  
 355    // Offs a callback (or several).
 356    // Uses an optimized counter if the listenee uses Backbone.Events.
 357    // Otherwise, falls back to manual tracking to support events
 358    // library interop.
 359    Listening.prototype.off = function(name, callback) {
 360      var cleanup;
 361      if (this.interop) {
 362        this._events = eventsApi(offApi, this._events, name, callback, {
 363          context: void 0,
 364          listeners: void 0
 365        });
 366        cleanup = !this._events;
 367      } else {
 368        this.count--;
 369        cleanup = this.count === 0;
 370      }
 371      if (cleanup) this.cleanup();
 372    };
 373  
 374    // Cleans up memory bindings between the listener and the listenee.
 375    Listening.prototype.cleanup = function() {
 376      delete this.listener._listeningTo[this.obj._listenId];
 377      if (!this.interop) delete this.obj._listeners[this.id];
 378    };
 379  
 380    // Aliases for backwards compatibility.
 381    Events.bind   = Events.on;
 382    Events.unbind = Events.off;
 383  
 384    // Allow the `Backbone` object to serve as a global event bus, for folks who
 385    // want global "pubsub" in a convenient place.
 386    _.extend(Backbone, Events);
 387  
 388    // Backbone.Model
 389    // --------------
 390  
 391    // Backbone **Models** are the basic data object in the framework --
 392    // frequently representing a row in a table in a database on your server.
 393    // A discrete chunk of data and a bunch of useful, related methods for
 394    // performing computations and transformations on that data.
 395  
 396    // Create a new model with the specified attributes. A client id (`cid`)
 397    // is automatically generated and assigned for you.
 398    var Model = Backbone.Model = function(attributes, options) {
 399      var attrs = attributes || {};
 400      options || (options = {});
 401      this.preinitialize.apply(this, arguments);
 402      this.cid = _.uniqueId(this.cidPrefix);
 403      this.attributes = {};
 404      if (options.collection) this.collection = options.collection;
 405      if (options.parse) attrs = this.parse(attrs, options) || {};
 406      var defaults = _.result(this, 'defaults');
 407  
 408      // Just _.defaults would work fine, but the additional _.extends
 409      // is in there for historical reasons. See #3843.
 410      attrs = _.defaults(_.extend({}, defaults, attrs), defaults);
 411  
 412      this.set(attrs, options);
 413      this.changed = {};
 414      this.initialize.apply(this, arguments);
 415    };
 416  
 417    // Attach all inheritable methods to the Model prototype.
 418    _.extend(Model.prototype, Events, {
 419  
 420      // A hash of attributes whose current and previous value differ.
 421      changed: null,
 422  
 423      // The value returned during the last failed validation.
 424      validationError: null,
 425  
 426      // The default name for the JSON `id` attribute is `"id"`. MongoDB and
 427      // CouchDB users may want to set this to `"_id"`.
 428      idAttribute: 'id',
 429  
 430      // The prefix is used to create the client id which is used to identify models locally.
 431      // You may want to override this if you're experiencing name clashes with model ids.
 432      cidPrefix: 'c',
 433  
 434      // preinitialize is an empty function by default. You can override it with a function
 435      // or object.  preinitialize will run before any instantiation logic is run in the Model.
 436      preinitialize: function(){},
 437  
 438      // Initialize is an empty function by default. Override it with your own
 439      // initialization logic.
 440      initialize: function(){},
 441  
 442      // Return a copy of the model's `attributes` object.
 443      toJSON: function(options) {
 444        return _.clone(this.attributes);
 445      },
 446  
 447      // Proxy `Backbone.sync` by default -- but override this if you need
 448      // custom syncing semantics for *this* particular model.
 449      sync: function() {
 450        return Backbone.sync.apply(this, arguments);
 451      },
 452  
 453      // Get the value of an attribute.
 454      get: function(attr) {
 455        return this.attributes[attr];
 456      },
 457  
 458      // Get the HTML-escaped value of an attribute.
 459      escape: function(attr) {
 460        return _.escape(this.get(attr));
 461      },
 462  
 463      // Returns `true` if the attribute contains a value that is not null
 464      // or undefined.
 465      has: function(attr) {
 466        return this.get(attr) != null;
 467      },
 468  
 469      // Special-cased proxy to underscore's `_.matches` method.
 470      matches: function(attrs) {
 471        return !!_.iteratee(attrs, this)(this.attributes);
 472      },
 473  
 474      // Set a hash of model attributes on the object, firing `"change"`. This is
 475      // the core primitive operation of a model, updating the data and notifying
 476      // anyone who needs to know about the change in state. The heart of the beast.
 477      set: function(key, val, options) {
 478        if (key == null) return this;
 479  
 480        // Handle both `"key", value` and `{key: value}` -style arguments.
 481        var attrs;
 482        if (typeof key === 'object') {
 483          attrs = key;
 484          options = val;
 485        } else {
 486          (attrs = {})[key] = val;
 487        }
 488  
 489        options || (options = {});
 490  
 491        // Run validation.
 492        if (!this._validate(attrs, options)) return false;
 493  
 494        // Extract attributes and options.
 495        var unset      = options.unset;
 496        var silent     = options.silent;
 497        var changes    = [];
 498        var changing   = this._changing;
 499        this._changing = true;
 500  
 501        if (!changing) {
 502          this._previousAttributes = _.clone(this.attributes);
 503          this.changed = {};
 504        }
 505  
 506        var current = this.attributes;
 507        var changed = this.changed;
 508        var prev    = this._previousAttributes;
 509  
 510        // For each `set` attribute, update or delete the current value.
 511        for (var attr in attrs) {
 512          val = attrs[attr];
 513          if (!_.isEqual(current[attr], val)) changes.push(attr);
 514          if (!_.isEqual(prev[attr], val)) {
 515            changed[attr] = val;
 516          } else {
 517            delete changed[attr];
 518          }
 519          unset ? delete current[attr] : current[attr] = val;
 520        }
 521  
 522        // Update the `id`.
 523        if (this.idAttribute in attrs) {
 524          var prevId = this.id;
 525          this.id = this.get(this.idAttribute);
 526          if (this.id !== prevId) {
 527            this.trigger('changeId', this, prevId, options);
 528          }
 529        }
 530  
 531        // Trigger all relevant attribute changes.
 532        if (!silent) {
 533          if (changes.length) this._pending = options;
 534          for (var i = 0; i < changes.length; i++) {
 535            this.trigger('change:' + changes[i], this, current[changes[i]], options);
 536          }
 537        }
 538  
 539        // You might be wondering why there's a `while` loop here. Changes can
 540        // be recursively nested within `"change"` events.
 541        if (changing) return this;
 542        if (!silent) {
 543          while (this._pending) {
 544            options = this._pending;
 545            this._pending = false;
 546            this.trigger('change', this, options);
 547          }
 548        }
 549        this._pending = false;
 550        this._changing = false;
 551        return this;
 552      },
 553  
 554      // Remove an attribute from the model, firing `"change"`. `unset` is a noop
 555      // if the attribute doesn't exist.
 556      unset: function(attr, options) {
 557        return this.set(attr, void 0, _.extend({}, options, {unset: true}));
 558      },
 559  
 560      // Clear all attributes on the model, firing `"change"`.
 561      clear: function(options) {
 562        var attrs = {};
 563        for (var key in this.attributes) attrs[key] = void 0;
 564        return this.set(attrs, _.extend({}, options, {unset: true}));
 565      },
 566  
 567      // Determine if the model has changed since the last `"change"` event.
 568      // If you specify an attribute name, determine if that attribute has changed.
 569      hasChanged: function(attr) {
 570        if (attr == null) return !_.isEmpty(this.changed);
 571        return _.has(this.changed, attr);
 572      },
 573  
 574      // Return an object containing all the attributes that have changed, or
 575      // false if there are no changed attributes. Useful for determining what
 576      // parts of a view need to be updated and/or what attributes need to be
 577      // persisted to the server. Unset attributes will be set to undefined.
 578      // You can also pass an attributes object to diff against the model,
 579      // determining if there *would be* a change.
 580      changedAttributes: function(diff) {
 581        if (!diff) return this.hasChanged() ? _.clone(this.changed) : false;
 582        var old = this._changing ? this._previousAttributes : this.attributes;
 583        var changed = {};
 584        var hasChanged;
 585        for (var attr in diff) {
 586          var val = diff[attr];
 587          if (_.isEqual(old[attr], val)) continue;
 588          changed[attr] = val;
 589          hasChanged = true;
 590        }
 591        return hasChanged ? changed : false;
 592      },
 593  
 594      // Get the previous value of an attribute, recorded at the time the last
 595      // `"change"` event was fired.
 596      previous: function(attr) {
 597        if (attr == null || !this._previousAttributes) return null;
 598        return this._previousAttributes[attr];
 599      },
 600  
 601      // Get all of the attributes of the model at the time of the previous
 602      // `"change"` event.
 603      previousAttributes: function() {
 604        return _.clone(this._previousAttributes);
 605      },
 606  
 607      // Fetch the model from the server, merging the response with the model's
 608      // local attributes. Any changed attributes will trigger a "change" event.
 609      fetch: function(options) {
 610        options = _.extend({parse: true}, options);
 611        var model = this;
 612        var success = options.success;
 613        options.success = function(resp) {
 614          var serverAttrs = options.parse ? model.parse(resp, options) : resp;
 615          if (!model.set(serverAttrs, options)) return false;
 616          if (success) success.call(options.context, model, resp, options);
 617          model.trigger('sync', model, resp, options);
 618        };
 619        wrapError(this, options);
 620        return this.sync('read', this, options);
 621      },
 622  
 623      // Set a hash of model attributes, and sync the model to the server.
 624      // If the server returns an attributes hash that differs, the model's
 625      // state will be `set` again.
 626      save: function(key, val, options) {
 627        // Handle both `"key", value` and `{key: value}` -style arguments.
 628        var attrs;
 629        if (key == null || typeof key === 'object') {
 630          attrs = key;
 631          options = val;
 632        } else {
 633          (attrs = {})[key] = val;
 634        }
 635  
 636        options = _.extend({validate: true, parse: true}, options);
 637        var wait = options.wait;
 638  
 639        // If we're not waiting and attributes exist, save acts as
 640        // `set(attr).save(null, opts)` with validation. Otherwise, check if
 641        // the model will be valid when the attributes, if any, are set.
 642        if (attrs && !wait) {
 643          if (!this.set(attrs, options)) return false;
 644        } else if (!this._validate(attrs, options)) {
 645          return false;
 646        }
 647  
 648        // After a successful server-side save, the client is (optionally)
 649        // updated with the server-side state.
 650        var model = this;
 651        var success = options.success;
 652        var attributes = this.attributes;
 653        options.success = function(resp) {
 654          // Ensure attributes are restored during synchronous saves.
 655          model.attributes = attributes;
 656          var serverAttrs = options.parse ? model.parse(resp, options) : resp;
 657          if (wait) serverAttrs = _.extend({}, attrs, serverAttrs);
 658          if (serverAttrs && !model.set(serverAttrs, options)) return false;
 659          if (success) success.call(options.context, model, resp, options);
 660          model.trigger('sync', model, resp, options);
 661        };
 662        wrapError(this, options);
 663  
 664        // Set temporary attributes if `{wait: true}` to properly find new ids.
 665        if (attrs && wait) this.attributes = _.extend({}, attributes, attrs);
 666  
 667        var method = this.isNew() ? 'create' : options.patch ? 'patch' : 'update';
 668        if (method === 'patch' && !options.attrs) options.attrs = attrs;
 669        var xhr = this.sync(method, this, options);
 670  
 671        // Restore attributes.
 672        this.attributes = attributes;
 673  
 674        return xhr;
 675      },
 676  
 677      // Destroy this model on the server if it was already persisted.
 678      // Optimistically removes the model from its collection, if it has one.
 679      // If `wait: true` is passed, waits for the server to respond before removal.
 680      destroy: function(options) {
 681        options = options ? _.clone(options) : {};
 682        var model = this;
 683        var success = options.success;
 684        var wait = options.wait;
 685  
 686        var destroy = function() {
 687          model.stopListening();
 688          model.trigger('destroy', model, model.collection, options);
 689        };
 690  
 691        options.success = function(resp) {
 692          if (wait) destroy();
 693          if (success) success.call(options.context, model, resp, options);
 694          if (!model.isNew()) model.trigger('sync', model, resp, options);
 695        };
 696  
 697        var xhr = false;
 698        if (this.isNew()) {
 699          _.defer(options.success);
 700        } else {
 701          wrapError(this, options);
 702          xhr = this.sync('delete', this, options);
 703        }
 704        if (!wait) destroy();
 705        return xhr;
 706      },
 707  
 708      // Default URL for the model's representation on the server -- if you're
 709      // using Backbone's restful methods, override this to change the endpoint
 710      // that will be called.
 711      url: function() {
 712        var base =
 713          _.result(this, 'urlRoot') ||
 714          _.result(this.collection, 'url') ||
 715          urlError();
 716        if (this.isNew()) return base;
 717        var id = this.get(this.idAttribute);
 718        return base.replace(/[^\/]$/, '$&/') + encodeURIComponent(id);
 719      },
 720  
 721      // **parse** converts a response into the hash of attributes to be `set` on
 722      // the model. The default implementation is just to pass the response along.
 723      parse: function(resp, options) {
 724        return resp;
 725      },
 726  
 727      // Create a new model with identical attributes to this one.
 728      clone: function() {
 729        return new this.constructor(this.attributes);
 730      },
 731  
 732      // A model is new if it has never been saved to the server, and lacks an id.
 733      isNew: function() {
 734        return !this.has(this.idAttribute);
 735      },
 736  
 737      // Check if the model is currently in a valid state.
 738      isValid: function(options) {
 739        return this._validate({}, _.extend({}, options, {validate: true}));
 740      },
 741  
 742      // Run validation against the next complete set of model attributes,
 743      // returning `true` if all is well. Otherwise, fire an `"invalid"` event.
 744      _validate: function(attrs, options) {
 745        if (!options.validate || !this.validate) return true;
 746        attrs = _.extend({}, this.attributes, attrs);
 747        var error = this.validationError = this.validate(attrs, options) || null;
 748        if (!error) return true;
 749        this.trigger('invalid', this, error, _.extend(options, {validationError: error}));
 750        return false;
 751      }
 752  
 753    });
 754  
 755    // Backbone.Collection
 756    // -------------------
 757  
 758    // If models tend to represent a single row of data, a Backbone Collection is
 759    // more analogous to a table full of data ... or a small slice or page of that
 760    // table, or a collection of rows that belong together for a particular reason
 761    // -- all of the messages in this particular folder, all of the documents
 762    // belonging to this particular author, and so on. Collections maintain
 763    // indexes of their models, both in order, and for lookup by `id`.
 764  
 765    // Create a new **Collection**, perhaps to contain a specific type of `model`.
 766    // If a `comparator` is specified, the Collection will maintain
 767    // its models in sort order, as they're added and removed.
 768    var Collection = Backbone.Collection = function(models, options) {
 769      options || (options = {});
 770      this.preinitialize.apply(this, arguments);
 771      if (options.model) this.model = options.model;
 772      if (options.comparator !== void 0) this.comparator = options.comparator;
 773      this._reset();
 774      this.initialize.apply(this, arguments);
 775      if (models) this.reset(models, _.extend({silent: true}, options));
 776    };
 777  
 778    // Default options for `Collection#set`.
 779    var setOptions = {add: true, remove: true, merge: true};
 780    var addOptions = {add: true, remove: false};
 781  
 782    // Splices `insert` into `array` at index `at`.
 783    var splice = function(array, insert, at) {
 784      at = Math.min(Math.max(at, 0), array.length);
 785      var tail = Array(array.length - at);
 786      var length = insert.length;
 787      var i;
 788      for (i = 0; i < tail.length; i++) tail[i] = array[i + at];
 789      for (i = 0; i < length; i++) array[i + at] = insert[i];
 790      for (i = 0; i < tail.length; i++) array[i + length + at] = tail[i];
 791    };
 792  
 793    // Define the Collection's inheritable methods.
 794    _.extend(Collection.prototype, Events, {
 795  
 796      // The default model for a collection is just a **Backbone.Model**.
 797      // This should be overridden in most cases.
 798      model: Model,
 799  
 800  
 801      // preinitialize is an empty function by default. You can override it with a function
 802      // or object.  preinitialize will run before any instantiation logic is run in the Collection.
 803      preinitialize: function(){},
 804  
 805      // Initialize is an empty function by default. Override it with your own
 806      // initialization logic.
 807      initialize: function(){},
 808  
 809      // The JSON representation of a Collection is an array of the
 810      // models' attributes.
 811      toJSON: function(options) {
 812        return this.map(function(model) { return model.toJSON(options); });
 813      },
 814  
 815      // Proxy `Backbone.sync` by default.
 816      sync: function() {
 817        return Backbone.sync.apply(this, arguments);
 818      },
 819  
 820      // Add a model, or list of models to the set. `models` may be Backbone
 821      // Models or raw JavaScript objects to be converted to Models, or any
 822      // combination of the two.
 823      add: function(models, options) {
 824        return this.set(models, _.extend({merge: false}, options, addOptions));
 825      },
 826  
 827      // Remove a model, or a list of models from the set.
 828      remove: function(models, options) {
 829        options = _.extend({}, options);
 830        var singular = !_.isArray(models);
 831        models = singular ? [models] : models.slice();
 832        var removed = this._removeModels(models, options);
 833        if (!options.silent && removed.length) {
 834          options.changes = {added: [], merged: [], removed: removed};
 835          this.trigger('update', this, options);
 836        }
 837        return singular ? removed[0] : removed;
 838      },
 839  
 840      // Update a collection by `set`-ing a new list of models, adding new ones,
 841      // removing models that are no longer present, and merging models that
 842      // already exist in the collection, as necessary. Similar to **Model#set**,
 843      // the core operation for updating the data contained by the collection.
 844      set: function(models, options) {
 845        if (models == null) return;
 846  
 847        options = _.extend({}, setOptions, options);
 848        if (options.parse && !this._isModel(models)) {
 849          models = this.parse(models, options) || [];
 850        }
 851  
 852        var singular = !_.isArray(models);
 853        models = singular ? [models] : models.slice();
 854  
 855        var at = options.at;
 856        if (at != null) at = +at;
 857        if (at > this.length) at = this.length;
 858        if (at < 0) at += this.length + 1;
 859  
 860        var set = [];
 861        var toAdd = [];
 862        var toMerge = [];
 863        var toRemove = [];
 864        var modelMap = {};
 865  
 866        var add = options.add;
 867        var merge = options.merge;
 868        var remove = options.remove;
 869  
 870        var sort = false;
 871        var sortable = this.comparator && at == null && options.sort !== false;
 872        var sortAttr = _.isString(this.comparator) ? this.comparator : null;
 873  
 874        // Turn bare objects into model references, and prevent invalid models
 875        // from being added.
 876        var model, i;
 877        for (i = 0; i < models.length; i++) {
 878          model = models[i];
 879  
 880          // If a duplicate is found, prevent it from being added and
 881          // optionally merge it into the existing model.
 882          var existing = this.get(model);
 883          if (existing) {
 884            if (merge && model !== existing) {
 885              var attrs = this._isModel(model) ? model.attributes : model;
 886              if (options.parse) attrs = existing.parse(attrs, options);
 887              existing.set(attrs, options);
 888              toMerge.push(existing);
 889              if (sortable && !sort) sort = existing.hasChanged(sortAttr);
 890            }
 891            if (!modelMap[existing.cid]) {
 892              modelMap[existing.cid] = true;
 893              set.push(existing);
 894            }
 895            models[i] = existing;
 896  
 897          // If this is a new, valid model, push it to the `toAdd` list.
 898          } else if (add) {
 899            model = models[i] = this._prepareModel(model, options);
 900            if (model) {
 901              toAdd.push(model);
 902              this._addReference(model, options);
 903              modelMap[model.cid] = true;
 904              set.push(model);
 905            }
 906          }
 907        }
 908  
 909        // Remove stale models.
 910        if (remove) {
 911          for (i = 0; i < this.length; i++) {
 912            model = this.models[i];
 913            if (!modelMap[model.cid]) toRemove.push(model);
 914          }
 915          if (toRemove.length) this._removeModels(toRemove, options);
 916        }
 917  
 918        // See if sorting is needed, update `length` and splice in new models.
 919        var orderChanged = false;
 920        var replace = !sortable && add && remove;
 921        if (set.length && replace) {
 922          orderChanged = this.length !== set.length || _.some(this.models, function(m, index) {
 923            return m !== set[index];
 924          });
 925          this.models.length = 0;
 926          splice(this.models, set, 0);
 927          this.length = this.models.length;
 928        } else if (toAdd.length) {
 929          if (sortable) sort = true;
 930          splice(this.models, toAdd, at == null ? this.length : at);
 931          this.length = this.models.length;
 932        }
 933  
 934        // Silently sort the collection if appropriate.
 935        if (sort) this.sort({silent: true});
 936  
 937        // Unless silenced, it's time to fire all appropriate add/sort/update events.
 938        if (!options.silent) {
 939          for (i = 0; i < toAdd.length; i++) {
 940            if (at != null) options.index = at + i;
 941            model = toAdd[i];
 942            model.trigger('add', model, this, options);
 943          }
 944          if (sort || orderChanged) this.trigger('sort', this, options);
 945          if (toAdd.length || toRemove.length || toMerge.length) {
 946            options.changes = {
 947              added: toAdd,
 948              removed: toRemove,
 949              merged: toMerge
 950            };
 951            this.trigger('update', this, options);
 952          }
 953        }
 954  
 955        // Return the added (or merged) model (or models).
 956        return singular ? models[0] : models;
 957      },
 958  
 959      // When you have more items than you want to add or remove individually,
 960      // you can reset the entire set with a new list of models, without firing
 961      // any granular `add` or `remove` events. Fires `reset` when finished.
 962      // Useful for bulk operations and optimizations.
 963      reset: function(models, options) {
 964        options = options ? _.clone(options) : {};
 965        for (var i = 0; i < this.models.length; i++) {
 966          this._removeReference(this.models[i], options);
 967        }
 968        options.previousModels = this.models;
 969        this._reset();
 970        models = this.add(models, _.extend({silent: true}, options));
 971        if (!options.silent) this.trigger('reset', this, options);
 972        return models;
 973      },
 974  
 975      // Add a model to the end of the collection.
 976      push: function(model, options) {
 977        return this.add(model, _.extend({at: this.length}, options));
 978      },
 979  
 980      // Remove a model from the end of the collection.
 981      pop: function(options) {
 982        var model = this.at(this.length - 1);
 983        return this.remove(model, options);
 984      },
 985  
 986      // Add a model to the beginning of the collection.
 987      unshift: function(model, options) {
 988        return this.add(model, _.extend({at: 0}, options));
 989      },
 990  
 991      // Remove a model from the beginning of the collection.
 992      shift: function(options) {
 993        var model = this.at(0);
 994        return this.remove(model, options);
 995      },
 996  
 997      // Slice out a sub-array of models from the collection.
 998      slice: function() {
 999        return slice.apply(this.models, arguments);
1000      },
1001  
1002      // Get a model from the set by id, cid, model object with id or cid
1003      // properties, or an attributes object that is transformed through modelId.
1004      get: function(obj) {
1005        if (obj == null) return void 0;
1006        return this._byId[obj] ||
1007          this._byId[this.modelId(this._isModel(obj) ? obj.attributes : obj, obj.idAttribute)] ||
1008          obj.cid && this._byId[obj.cid];
1009      },
1010  
1011      // Returns `true` if the model is in the collection.
1012      has: function(obj) {
1013        return this.get(obj) != null;
1014      },
1015  
1016      // Get the model at the given index.
1017      at: function(index) {
1018        if (index < 0) index += this.length;
1019        return this.models[index];
1020      },
1021  
1022      // Return models with matching attributes. Useful for simple cases of
1023      // `filter`.
1024      where: function(attrs, first) {
1025        return this[first ? 'find' : 'filter'](attrs);
1026      },
1027  
1028      // Return the first model with matching attributes. Useful for simple cases
1029      // of `find`.
1030      findWhere: function(attrs) {
1031        return this.where(attrs, true);
1032      },
1033  
1034      // Force the collection to re-sort itself. You don't need to call this under
1035      // normal circumstances, as the set will maintain sort order as each item
1036      // is added.
1037      sort: function(options) {
1038        var comparator = this.comparator;
1039        if (!comparator) throw new Error('Cannot sort a set without a comparator');
1040        options || (options = {});
1041  
1042        var length = comparator.length;
1043        if (_.isFunction(comparator)) comparator = comparator.bind(this);
1044  
1045        // Run sort based on type of `comparator`.
1046        if (length === 1 || _.isString(comparator)) {
1047          this.models = this.sortBy(comparator);
1048        } else {
1049          this.models.sort(comparator);
1050        }
1051        if (!options.silent) this.trigger('sort', this, options);
1052        return this;
1053      },
1054  
1055      // Pluck an attribute from each model in the collection.
1056      pluck: function(attr) {
1057        return this.map(attr + '');
1058      },
1059  
1060      // Fetch the default set of models for this collection, resetting the
1061      // collection when they arrive. If `reset: true` is passed, the response
1062      // data will be passed through the `reset` method instead of `set`.
1063      fetch: function(options) {
1064        options = _.extend({parse: true}, options);
1065        var success = options.success;
1066        var collection = this;
1067        options.success = function(resp) {
1068          var method = options.reset ? 'reset' : 'set';
1069          collection[method](resp, options);
1070          if (success) success.call(options.context, collection, resp, options);
1071          collection.trigger('sync', collection, resp, options);
1072        };
1073        wrapError(this, options);
1074        return this.sync('read', this, options);
1075      },
1076  
1077      // Create a new instance of a model in this collection. Add the model to the
1078      // collection immediately, unless `wait: true` is passed, in which case we
1079      // wait for the server to agree.
1080      create: function(model, options) {
1081        options = options ? _.clone(options) : {};
1082        var wait = options.wait;
1083        model = this._prepareModel(model, options);
1084        if (!model) return false;
1085        if (!wait) this.add(model, options);
1086        var collection = this;
1087        var success = options.success;
1088        options.success = function(m, resp, callbackOpts) {
1089          if (wait) {
1090            m.off('error', collection._forwardPristineError, collection);
1091            collection.add(m, callbackOpts);
1092          }
1093          if (success) success.call(callbackOpts.context, m, resp, callbackOpts);
1094        };
1095        // In case of wait:true, our collection is not listening to any
1096        // of the model's events yet, so it will not forward the error
1097        // event. In this special case, we need to listen for it
1098        // separately and handle the event just once.
1099        // (The reason we don't need to do this for the sync event is
1100        // in the success handler above: we add the model first, which
1101        // causes the collection to listen, and then invoke the callback
1102        // that triggers the event.)
1103        if (wait) {
1104          model.once('error', this._forwardPristineError, this);
1105        }
1106        model.save(null, options);
1107        return model;
1108      },
1109  
1110      // **parse** converts a response into a list of models to be added to the
1111      // collection. The default implementation is just to pass it through.
1112      parse: function(resp, options) {
1113        return resp;
1114      },
1115  
1116      // Create a new collection with an identical list of models as this one.
1117      clone: function() {
1118        return new this.constructor(this.models, {
1119          model: this.model,
1120          comparator: this.comparator
1121        });
1122      },
1123  
1124      // Define how to uniquely identify models in the collection.
1125      modelId: function(attrs, idAttribute) {
1126        return attrs[idAttribute || this.model.prototype.idAttribute || 'id'];
1127      },
1128  
1129      // Get an iterator of all models in this collection.
1130      values: function() {
1131        return new CollectionIterator(this, ITERATOR_VALUES);
1132      },
1133  
1134      // Get an iterator of all model IDs in this collection.
1135      keys: function() {
1136        return new CollectionIterator(this, ITERATOR_KEYS);
1137      },
1138  
1139      // Get an iterator of all [ID, model] tuples in this collection.
1140      entries: function() {
1141        return new CollectionIterator(this, ITERATOR_KEYSVALUES);
1142      },
1143  
1144      // Private method to reset all internal state. Called when the collection
1145      // is first initialized or reset.
1146      _reset: function() {
1147        this.length = 0;
1148        this.models = [];
1149        this._byId  = {};
1150      },
1151  
1152      // Prepare a hash of attributes (or other model) to be added to this
1153      // collection.
1154      _prepareModel: function(attrs, options) {
1155        if (this._isModel(attrs)) {
1156          if (!attrs.collection) attrs.collection = this;
1157          return attrs;
1158        }
1159        options = options ? _.clone(options) : {};
1160        options.collection = this;
1161  
1162        var model;
1163        if (this.model.prototype) {
1164          model = new this.model(attrs, options);
1165        } else {
1166          // ES class methods didn't have prototype
1167          model = this.model(attrs, options);
1168        }
1169  
1170        if (!model.validationError) return model;
1171        this.trigger('invalid', this, model.validationError, options);
1172        return false;
1173      },
1174  
1175      // Internal method called by both remove and set.
1176      _removeModels: function(models, options) {
1177        var removed = [];
1178        for (var i = 0; i < models.length; i++) {
1179          var model = this.get(models[i]);
1180          if (!model) continue;
1181  
1182          var index = this.indexOf(model);
1183          this.models.splice(index, 1);
1184          this.length--;
1185  
1186          // Remove references before triggering 'remove' event to prevent an
1187          // infinite loop. #3693
1188          delete this._byId[model.cid];
1189          var id = this.modelId(model.attributes, model.idAttribute);
1190          if (id != null) delete this._byId[id];
1191  
1192          if (!options.silent) {
1193            options.index = index;
1194            model.trigger('remove', model, this, options);
1195          }
1196  
1197          removed.push(model);
1198          this._removeReference(model, options);
1199        }
1200        if (models.length > 0 && !options.silent) delete options.index;
1201        return removed;
1202      },
1203  
1204      // Method for checking whether an object should be considered a model for
1205      // the purposes of adding to the collection.
1206      _isModel: function(model) {
1207        return model instanceof Model;
1208      },
1209  
1210      // Internal method to create a model's ties to a collection.
1211      _addReference: function(model, options) {
1212        this._byId[model.cid] = model;
1213        var id = this.modelId(model.attributes, model.idAttribute);
1214        if (id != null) this._byId[id] = model;
1215        model.on('all', this._onModelEvent, this);
1216      },
1217  
1218      // Internal method to sever a model's ties to a collection.
1219      _removeReference: function(model, options) {
1220        delete this._byId[model.cid];
1221        var id = this.modelId(model.attributes, model.idAttribute);
1222        if (id != null) delete this._byId[id];
1223        if (this === model.collection) delete model.collection;
1224        model.off('all', this._onModelEvent, this);
1225      },
1226  
1227      // Internal method called every time a model in the set fires an event.
1228      // Sets need to update their indexes when models change ids. All other
1229      // events simply proxy through. "add" and "remove" events that originate
1230      // in other collections are ignored.
1231      _onModelEvent: function(event, model, collection, options) {
1232        if (model) {
1233          if ((event === 'add' || event === 'remove') && collection !== this) return;
1234          if (event === 'destroy') this.remove(model, options);
1235          if (event === 'changeId') {
1236            var prevId = this.modelId(model.previousAttributes(), model.idAttribute);
1237            var id = this.modelId(model.attributes, model.idAttribute);
1238            if (prevId != null) delete this._byId[prevId];
1239            if (id != null) this._byId[id] = model;
1240          }
1241        }
1242        this.trigger.apply(this, arguments);
1243      },
1244  
1245      // Internal callback method used in `create`. It serves as a
1246      // stand-in for the `_onModelEvent` method, which is not yet bound
1247      // during the `wait` period of the `create` call. We still want to
1248      // forward any `'error'` event at the end of the `wait` period,
1249      // hence a customized callback.
1250      _forwardPristineError: function(model, collection, options) {
1251        // Prevent double forward if the model was already in the
1252        // collection before the call to `create`.
1253        if (this.has(model)) return;
1254        this._onModelEvent('error', model, collection, options);
1255      }
1256    });
1257  
1258    // Defining an @@iterator method implements JavaScript's Iterable protocol.
1259    // In modern ES2015 browsers, this value is found at Symbol.iterator.
1260    /* global Symbol */
1261    var $$iterator = typeof Symbol === 'function' && Symbol.iterator;
1262    if ($$iterator) {
1263      Collection.prototype[$$iterator] = Collection.prototype.values;
1264    }
1265  
1266    // CollectionIterator
1267    // ------------------
1268  
1269    // A CollectionIterator implements JavaScript's Iterator protocol, allowing the
1270    // use of `for of` loops in modern browsers and interoperation between
1271    // Backbone.Collection and other JavaScript functions and third-party libraries
1272    // which can operate on Iterables.
1273    var CollectionIterator = function(collection, kind) {
1274      this._collection = collection;
1275      this._kind = kind;
1276      this._index = 0;
1277    };
1278  
1279    // This "enum" defines the three possible kinds of values which can be emitted
1280    // by a CollectionIterator that correspond to the values(), keys() and entries()
1281    // methods on Collection, respectively.
1282    var ITERATOR_VALUES = 1;
1283    var ITERATOR_KEYS = 2;
1284    var ITERATOR_KEYSVALUES = 3;
1285  
1286    // All Iterators should themselves be Iterable.
1287    if ($$iterator) {
1288      CollectionIterator.prototype[$$iterator] = function() {
1289        return this;
1290      };
1291    }
1292  
1293    CollectionIterator.prototype.next = function() {
1294      if (this._collection) {
1295  
1296        // Only continue iterating if the iterated collection is long enough.
1297        if (this._index < this._collection.length) {
1298          var model = this._collection.at(this._index);
1299          this._index++;
1300  
1301          // Construct a value depending on what kind of values should be iterated.
1302          var value;
1303          if (this._kind === ITERATOR_VALUES) {
1304            value = model;
1305          } else {
1306            var id = this._collection.modelId(model.attributes, model.idAttribute);
1307            if (this._kind === ITERATOR_KEYS) {
1308              value = id;
1309            } else { // ITERATOR_KEYSVALUES
1310              value = [id, model];
1311            }
1312          }
1313          return {value: value, done: false};
1314        }
1315  
1316        // Once exhausted, remove the reference to the collection so future
1317        // calls to the next method always return done.
1318        this._collection = void 0;
1319      }
1320  
1321      return {value: void 0, done: true};
1322    };
1323  
1324    // Backbone.View
1325    // -------------
1326  
1327    // Backbone Views are almost more convention than they are actual code. A View
1328    // is simply a JavaScript object that represents a logical chunk of UI in the
1329    // DOM. This might be a single item, an entire list, a sidebar or panel, or
1330    // even the surrounding frame which wraps your whole app. Defining a chunk of
1331    // UI as a **View** allows you to define your DOM events declaratively, without
1332    // having to worry about render order ... and makes it easy for the view to
1333    // react to specific changes in the state of your models.
1334  
1335    // Creating a Backbone.View creates its initial element outside of the DOM,
1336    // if an existing element is not provided...
1337    var View = Backbone.View = function(options) {
1338      this.cid = _.uniqueId('view');
1339      this.preinitialize.apply(this, arguments);
1340      _.extend(this, _.pick(options, viewOptions));
1341      this._ensureElement();
1342      this.initialize.apply(this, arguments);
1343    };
1344  
1345    // Cached regex to split keys for `delegate`.
1346    var delegateEventSplitter = /^(\S+)\s*(.*)$/;
1347  
1348    // List of view options to be set as properties.
1349    var viewOptions = ['model', 'collection', 'el', 'id', 'attributes', 'className', 'tagName', 'events'];
1350  
1351    // Set up all inheritable **Backbone.View** properties and methods.
1352    _.extend(View.prototype, Events, {
1353  
1354      // The default `tagName` of a View's element is `"div"`.
1355      tagName: 'div',
1356  
1357      // jQuery delegate for element lookup, scoped to DOM elements within the
1358      // current view. This should be preferred to global lookups where possible.
1359      $: function(selector) {
1360        return this.$el.find(selector);
1361      },
1362  
1363      // preinitialize is an empty function by default. You can override it with a function
1364      // or object.  preinitialize will run before any instantiation logic is run in the View
1365      preinitialize: function(){},
1366  
1367      // Initialize is an empty function by default. Override it with your own
1368      // initialization logic.
1369      initialize: function(){},
1370  
1371      // **render** is the core function that your view should override, in order
1372      // to populate its element (`this.el`), with the appropriate HTML. The
1373      // convention is for **render** to always return `this`.
1374      render: function() {
1375        return this;
1376      },
1377  
1378      // Remove this view by taking the element out of the DOM, and removing any
1379      // applicable Backbone.Events listeners.
1380      remove: function() {
1381        this._removeElement();
1382        this.stopListening();
1383        return this;
1384      },
1385  
1386      // Remove this view's element from the document and all event listeners
1387      // attached to it. Exposed for subclasses using an alternative DOM
1388      // manipulation API.
1389      _removeElement: function() {
1390        this.$el.remove();
1391      },
1392  
1393      // Change the view's element (`this.el` property) and re-delegate the
1394      // view's events on the new element.
1395      setElement: function(element) {
1396        this.undelegateEvents();
1397        this._setElement(element);
1398        this.delegateEvents();
1399        return this;
1400      },
1401  
1402      // Creates the `this.el` and `this.$el` references for this view using the
1403      // given `el`. `el` can be a CSS selector or an HTML string, a jQuery
1404      // context or an element. Subclasses can override this to utilize an
1405      // alternative DOM manipulation API and are only required to set the
1406      // `this.el` property.
1407      _setElement: function(el) {
1408        this.$el = el instanceof Backbone.$ ? el : Backbone.$(el);
1409        this.el = this.$el[0];
1410      },
1411  
1412      // Set callbacks, where `this.events` is a hash of
1413      //
1414      // *{"event selector": "callback"}*
1415      //
1416      //     {
1417      //       'mousedown .title':  'edit',
1418      //       'click .button':     'save',
1419      //       'click .open':       function(e) { ... }
1420      //     }
1421      //
1422      // pairs. Callbacks will be bound to the view, with `this` set properly.
1423      // Uses event delegation for efficiency.
1424      // Omitting the selector binds the event to `this.el`.
1425      delegateEvents: function(events) {
1426        events || (events = _.result(this, 'events'));
1427        if (!events) return this;
1428        this.undelegateEvents();
1429        for (var key in events) {
1430          var method = events[key];
1431          if (!_.isFunction(method)) method = this[method];
1432          if (!method) continue;
1433          var match = key.match(delegateEventSplitter);
1434          this.delegate(match[1], match[2], method.bind(this));
1435        }
1436        return this;
1437      },
1438  
1439      // Add a single event listener to the view's element (or a child element
1440      // using `selector`). This only works for delegate-able events: not `focus`,
1441      // `blur`, and not `change`, `submit`, and `reset` in Internet Explorer.
1442      delegate: function(eventName, selector, listener) {
1443        this.$el.on(eventName + '.delegateEvents' + this.cid, selector, listener);
1444        return this;
1445      },
1446  
1447      // Clears all callbacks previously bound to the view by `delegateEvents`.
1448      // You usually don't need to use this, but may wish to if you have multiple
1449      // Backbone views attached to the same DOM element.
1450      undelegateEvents: function() {
1451        if (this.$el) this.$el.off('.delegateEvents' + this.cid);
1452        return this;
1453      },
1454  
1455      // A finer-grained `undelegateEvents` for removing a single delegated event.
1456      // `selector` and `listener` are both optional.
1457      undelegate: function(eventName, selector, listener) {
1458        this.$el.off(eventName + '.delegateEvents' + this.cid, selector, listener);
1459        return this;
1460      },
1461  
1462      // Produces a DOM element to be assigned to your view. Exposed for
1463      // subclasses using an alternative DOM manipulation API.
1464      _createElement: function(tagName) {
1465        return document.createElement(tagName);
1466      },
1467  
1468      // Ensure that the View has a DOM element to render into.
1469      // If `this.el` is a string, pass it through `$()`, take the first
1470      // matching element, and re-assign it to `el`. Otherwise, create
1471      // an element from the `id`, `className` and `tagName` properties.
1472      _ensureElement: function() {
1473        if (!this.el) {
1474          var attrs = _.extend({}, _.result(this, 'attributes'));
1475          if (this.id) attrs.id = _.result(this, 'id');
1476          if (this.className) attrs['class'] = _.result(this, 'className');
1477          this.setElement(this._createElement(_.result(this, 'tagName')));
1478          this._setAttributes(attrs);
1479        } else {
1480          this.setElement(_.result(this, 'el'));
1481        }
1482      },
1483  
1484      // Set attributes from a hash on this view's element.  Exposed for
1485      // subclasses using an alternative DOM manipulation API.
1486      _setAttributes: function(attributes) {
1487        this.$el.attr(attributes);
1488      }
1489  
1490    });
1491  
1492    // Proxy Backbone class methods to Underscore functions, wrapping the model's
1493    // `attributes` object or collection's `models` array behind the scenes.
1494    //
1495    // collection.filter(function(model) { return model.get('age') > 10 });
1496    // collection.each(this.addView);
1497    //
1498    // `Function#apply` can be slow so we use the method's arg count, if we know it.
1499    var addMethod = function(base, length, method, attribute) {
1500      switch (length) {
1501        case 1: return function() {
1502          return base[method](this[attribute]);
1503        };
1504        case 2: return function(value) {
1505          return base[method](this[attribute], value);
1506        };
1507        case 3: return function(iteratee, context) {
1508          return base[method](this[attribute], cb(iteratee, this), context);
1509        };
1510        case 4: return function(iteratee, defaultVal, context) {
1511          return base[method](this[attribute], cb(iteratee, this), defaultVal, context);
1512        };
1513        default: return function() {
1514          var args = slice.call(arguments);
1515          args.unshift(this[attribute]);
1516          return base[method].apply(base, args);
1517        };
1518      }
1519    };
1520  
1521    var addUnderscoreMethods = function(Class, base, methods, attribute) {
1522      _.each(methods, function(length, method) {
1523        if (base[method]) Class.prototype[method] = addMethod(base, length, method, attribute);
1524      });
1525    };
1526  
1527    // Support `collection.sortBy('attr')` and `collection.findWhere({id: 1})`.
1528    var cb = function(iteratee, instance) {
1529      if (_.isFunction(iteratee)) return iteratee;
1530      if (_.isObject(iteratee) && !instance._isModel(iteratee)) return modelMatcher(iteratee);
1531      if (_.isString(iteratee)) return function(model) { return model.get(iteratee); };
1532      return iteratee;
1533    };
1534    var modelMatcher = function(attrs) {
1535      var matcher = _.matches(attrs);
1536      return function(model) {
1537        return matcher(model.attributes);
1538      };
1539    };
1540  
1541    // Underscore methods that we want to implement on the Collection.
1542    // 90% of the core usefulness of Backbone Collections is actually implemented
1543    // right here:
1544    var collectionMethods = {forEach: 3, each: 3, map: 3, collect: 3, reduce: 0,
1545      foldl: 0, inject: 0, reduceRight: 0, foldr: 0, find: 3, detect: 3, filter: 3,
1546      select: 3, reject: 3, every: 3, all: 3, some: 3, any: 3, include: 3, includes: 3,
1547      contains: 3, invoke: 0, max: 3, min: 3, toArray: 1, size: 1, first: 3,
1548      head: 3, take: 3, initial: 3, rest: 3, tail: 3, drop: 3, last: 3,
1549      without: 0, difference: 0, indexOf: 3, shuffle: 1, lastIndexOf: 3,
1550      isEmpty: 1, chain: 1, sample: 3, partition: 3, groupBy: 3, countBy: 3,
1551      sortBy: 3, indexBy: 3, findIndex: 3, findLastIndex: 3};
1552  
1553  
1554    // Underscore methods that we want to implement on the Model, mapped to the
1555    // number of arguments they take.
1556    var modelMethods = {keys: 1, values: 1, pairs: 1, invert: 1, pick: 0,
1557      omit: 0, chain: 1, isEmpty: 1};
1558  
1559    // Mix in each Underscore method as a proxy to `Collection#models`.
1560  
1561    _.each([
1562      [Collection, collectionMethods, 'models'],
1563      [Model, modelMethods, 'attributes']
1564    ], function(config) {
1565      var Base = config[0],
1566          methods = config[1],
1567          attribute = config[2];
1568  
1569      Base.mixin = function(obj) {
1570        var mappings = _.reduce(_.functions(obj), function(memo, name) {
1571          memo[name] = 0;
1572          return memo;
1573        }, {});
1574        addUnderscoreMethods(Base, obj, mappings, attribute);
1575      };
1576  
1577      addUnderscoreMethods(Base, _, methods, attribute);
1578    });
1579  
1580    // Backbone.sync
1581    // -------------
1582  
1583    // Override this function to change the manner in which Backbone persists
1584    // models to the server. You will be passed the type of request, and the
1585    // model in question. By default, makes a RESTful Ajax request
1586    // to the model's `url()`. Some possible customizations could be:
1587    //
1588    // * Use `setTimeout` to batch rapid-fire updates into a single request.
1589    // * Send up the models as XML instead of JSON.
1590    // * Persist models via WebSockets instead of Ajax.
1591    //
1592    // Turn on `Backbone.emulateHTTP` in order to send `PUT` and `DELETE` requests
1593    // as `POST`, with a `_method` parameter containing the true HTTP method,
1594    // as well as all requests with the body as `application/x-www-form-urlencoded`
1595    // instead of `application/json` with the model in a param named `model`.
1596    // Useful when interfacing with server-side languages like **PHP** that make
1597    // it difficult to read the body of `PUT` requests.
1598    Backbone.sync = function(method, model, options) {
1599      var type = methodMap[method];
1600  
1601      // Default options, unless specified.
1602      _.defaults(options || (options = {}), {
1603        emulateHTTP: Backbone.emulateHTTP,
1604        emulateJSON: Backbone.emulateJSON
1605      });
1606  
1607      // Default JSON-request options.
1608      var params = {type: type, dataType: 'json'};
1609  
1610      // Ensure that we have a URL.
1611      if (!options.url) {
1612        params.url = _.result(model, 'url') || urlError();
1613      }
1614  
1615      // Ensure that we have the appropriate request data.
1616      if (options.data == null && model && (method === 'create' || method === 'update' || method === 'patch')) {
1617        params.contentType = 'application/json';
1618        params.data = JSON.stringify(options.attrs || model.toJSON(options));
1619      }
1620  
1621      // For older servers, emulate JSON by encoding the request into an HTML-form.
1622      if (options.emulateJSON) {
1623        params.contentType = 'application/x-www-form-urlencoded';
1624        params.data = params.data ? {model: params.data} : {};
1625      }
1626  
1627      // For older servers, emulate HTTP by mimicking the HTTP method with `_method`
1628      // And an `X-HTTP-Method-Override` header.
1629      if (options.emulateHTTP && (type === 'PUT' || type === 'DELETE' || type === 'PATCH')) {
1630        params.type = 'POST';
1631        if (options.emulateJSON) params.data._method = type;
1632        var beforeSend = options.beforeSend;
1633        options.beforeSend = function(xhr) {
1634          xhr.setRequestHeader('X-HTTP-Method-Override', type);
1635          if (beforeSend) return beforeSend.apply(this, arguments);
1636        };
1637      }
1638  
1639      // Don't process data on a non-GET request.
1640      if (params.type !== 'GET' && !options.emulateJSON) {
1641        params.processData = false;
1642      }
1643  
1644      // Pass along `textStatus` and `errorThrown` from jQuery.
1645      var error = options.error;
1646      options.error = function(xhr, textStatus, errorThrown) {
1647        options.textStatus = textStatus;
1648        options.errorThrown = errorThrown;
1649        if (error) error.call(options.context, xhr, textStatus, errorThrown);
1650      };
1651  
1652      // Make the request, allowing the user to override any Ajax options.
1653      var xhr = options.xhr = Backbone.ajax(_.extend(params, options));
1654      model.trigger('request', model, xhr, options);
1655      return xhr;
1656    };
1657  
1658    // Map from CRUD to HTTP for our default `Backbone.sync` implementation.
1659    var methodMap = {
1660      'create': 'POST',
1661      'update': 'PUT',
1662      'patch': 'PATCH',
1663      'delete': 'DELETE',
1664      'read': 'GET'
1665    };
1666  
1667    // Set the default implementation of `Backbone.ajax` to proxy through to `$`.
1668    // Override this if you'd like to use a different library.
1669    Backbone.ajax = function() {
1670      return Backbone.$.ajax.apply(Backbone.$, arguments);
1671    };
1672  
1673    // Backbone.Router
1674    // ---------------
1675  
1676    // Routers map faux-URLs to actions, and fire events when routes are
1677    // matched. Creating a new one sets its `routes` hash, if not set statically.
1678    var Router = Backbone.Router = function(options) {
1679      options || (options = {});
1680      this.preinitialize.apply(this, arguments);
1681      if (options.routes) this.routes = options.routes;
1682      this._bindRoutes();
1683      this.initialize.apply(this, arguments);
1684    };
1685  
1686    // Cached regular expressions for matching named param parts and splatted
1687    // parts of route strings.
1688    var optionalParam = /\((.*?)\)/g;
1689    var namedParam    = /(\(\?)?:\w+/g;
1690    var splatParam    = /\*\w+/g;
1691    var escapeRegExp  = /[\-{}\[\]+?.,\\\^$|#\s]/g;
1692  
1693    // Set up all inheritable **Backbone.Router** properties and methods.
1694    _.extend(Router.prototype, Events, {
1695  
1696      // preinitialize is an empty function by default. You can override it with a function
1697      // or object.  preinitialize will run before any instantiation logic is run in the Router.
1698      preinitialize: function(){},
1699  
1700      // Initialize is an empty function by default. Override it with your own
1701      // initialization logic.
1702      initialize: function(){},
1703  
1704      // Manually bind a single named route to a callback. For example:
1705      //
1706      //     this.route('search/:query/p:num', 'search', function(query, num) {
1707      //       ...
1708      //     });
1709      //
1710      route: function(route, name, callback) {
1711        if (!_.isRegExp(route)) route = this._routeToRegExp(route);
1712        if (_.isFunction(name)) {
1713          callback = name;
1714          name = '';
1715        }
1716        if (!callback) callback = this[name];
1717        var router = this;
1718        Backbone.history.route(route, function(fragment) {
1719          var args = router._extractParameters(route, fragment);
1720          if (router.execute(callback, args, name) !== false) {
1721            router.trigger.apply(router, ['route:' + name].concat(args));
1722            router.trigger('route', name, args);
1723            Backbone.history.trigger('route', router, name, args);
1724          }
1725        });
1726        return this;
1727      },
1728  
1729      // Execute a route handler with the provided parameters.  This is an
1730      // excellent place to do pre-route setup or post-route cleanup.
1731      execute: function(callback, args, name) {
1732        if (callback) callback.apply(this, args);
1733      },
1734  
1735      // Simple proxy to `Backbone.history` to save a fragment into the history.
1736      navigate: function(fragment, options) {
1737        Backbone.history.navigate(fragment, options);
1738        return this;
1739      },
1740  
1741      // Bind all defined routes to `Backbone.history`. We have to reverse the
1742      // order of the routes here to support behavior where the most general
1743      // routes can be defined at the bottom of the route map.
1744      _bindRoutes: function() {
1745        if (!this.routes) return;
1746        this.routes = _.result(this, 'routes');
1747        var route, routes = _.keys(this.routes);
1748        while ((route = routes.pop()) != null) {
1749          this.route(route, this.routes[route]);
1750        }
1751      },
1752  
1753      // Convert a route string into a regular expression, suitable for matching
1754      // against the current location hash.
1755      _routeToRegExp: function(route) {
1756        route = route.replace(escapeRegExp, '\\$&')
1757        .replace(optionalParam, '(?:$1)?')
1758        .replace(namedParam, function(match, optional) {
1759          return optional ? match : '([^/?]+)';
1760        })
1761        .replace(splatParam, '([^?]*?)');
1762        return new RegExp('^' + route + '(?:\\?([\\s\\S]*))?$');
1763      },
1764  
1765      // Given a route, and a URL fragment that it matches, return the array of
1766      // extracted decoded parameters. Empty or unmatched parameters will be
1767      // treated as `null` to normalize cross-browser behavior.
1768      _extractParameters: function(route, fragment) {
1769        var params = route.exec(fragment).slice(1);
1770        return _.map(params, function(param, i) {
1771          // Don't decode the search params.
1772          if (i === params.length - 1) return param || null;
1773          return param ? decodeURIComponent(param) : null;
1774        });
1775      }
1776  
1777    });
1778  
1779    // Backbone.History
1780    // ----------------
1781  
1782    // Handles cross-browser history management, based on either
1783    // [pushState](http://diveintohtml5.info/history.html) and real URLs, or
1784    // [onhashchange](https://developer.mozilla.org/en-US/docs/DOM/window.onhashchange)
1785    // and URL fragments. If the browser supports neither (old IE, natch),
1786    // falls back to polling.
1787    var History = Backbone.History = function() {
1788      this.handlers = [];
1789      this.checkUrl = this.checkUrl.bind(this);
1790  
1791      // Ensure that `History` can be used outside of the browser.
1792      if (typeof window !== 'undefined') {
1793        this.location = window.location;
1794        this.history = window.history;
1795      }
1796    };
1797  
1798    // Cached regex for stripping a leading hash/slash and trailing space.
1799    var routeStripper = /^[#\/]|\s+$/g;
1800  
1801    // Cached regex for stripping leading and trailing slashes.
1802    var rootStripper = /^\/+|\/+$/g;
1803  
1804    // Cached regex for stripping urls of hash.
1805    var pathStripper = /#.*$/;
1806  
1807    // Has the history handling already been started?
1808    History.started = false;
1809  
1810    // Set up all inheritable **Backbone.History** properties and methods.
1811    _.extend(History.prototype, Events, {
1812  
1813      // The default interval to poll for hash changes, if necessary, is
1814      // twenty times a second.
1815      interval: 50,
1816  
1817      // Are we at the app root?
1818      atRoot: function() {
1819        var path = this.location.pathname.replace(/[^\/]$/, '$&/');
1820        return path === this.root && !this.getSearch();
1821      },
1822  
1823      // Does the pathname match the root?
1824      matchRoot: function() {
1825        var path = this.decodeFragment(this.location.pathname);
1826        var rootPath = path.slice(0, this.root.length - 1) + '/';
1827        return rootPath === this.root;
1828      },
1829  
1830      // Unicode characters in `location.pathname` are percent encoded so they're
1831      // decoded for comparison. `%25` should not be decoded since it may be part
1832      // of an encoded parameter.
1833      decodeFragment: function(fragment) {
1834        return decodeURI(fragment.replace(/%25/g, '%2525'));
1835      },
1836  
1837      // In IE6, the hash fragment and search params are incorrect if the
1838      // fragment contains `?`.
1839      getSearch: function() {
1840        var match = this.location.href.replace(/#.*/, '').match(/\?.+/);
1841        return match ? match[0] : '';
1842      },
1843  
1844      // Gets the true hash value. Cannot use location.hash directly due to bug
1845      // in Firefox where location.hash will always be decoded.
1846      getHash: function(window) {
1847        var match = (window || this).location.href.match(/#(.*)$/);
1848        return match ? match[1] : '';
1849      },
1850  
1851      // Get the pathname and search params, without the root.
1852      getPath: function() {
1853        var path = this.decodeFragment(
1854          this.location.pathname + this.getSearch()
1855        ).slice(this.root.length - 1);
1856        return path.charAt(0) === '/' ? path.slice(1) : path;
1857      },
1858  
1859      // Get the cross-browser normalized URL fragment from the path or hash.
1860      getFragment: function(fragment) {
1861        if (fragment == null) {
1862          if (this._usePushState || !this._wantsHashChange) {
1863            fragment = this.getPath();
1864          } else {
1865            fragment = this.getHash();
1866          }
1867        }
1868        return fragment.replace(routeStripper, '');
1869      },
1870  
1871      // Start the hash change handling, returning `true` if the current URL matches
1872      // an existing route, and `false` otherwise.
1873      start: function(options) {
1874        if (History.started) throw new Error('Backbone.history has already been started');
1875        History.started = true;
1876  
1877        // Figure out the initial configuration. Do we need an iframe?
1878        // Is pushState desired ... is it available?
1879        this.options          = _.extend({root: '/'}, this.options, options);
1880        this.root             = this.options.root;
1881        this._trailingSlash   = this.options.trailingSlash;
1882        this._wantsHashChange = this.options.hashChange !== false;
1883        this._hasHashChange   = 'onhashchange' in window && (document.documentMode === void 0 || document.documentMode > 7);
1884        this._useHashChange   = this._wantsHashChange && this._hasHashChange;
1885        this._wantsPushState  = !!this.options.pushState;
1886        this._hasPushState    = !!(this.history && this.history.pushState);
1887        this._usePushState    = this._wantsPushState && this._hasPushState;
1888        this.fragment         = this.getFragment();
1889  
1890        // Normalize root to always include a leading and trailing slash.
1891        this.root = ('/' + this.root + '/').replace(rootStripper, '/');
1892  
1893        // Transition from hashChange to pushState or vice versa if both are
1894        // requested.
1895        if (this._wantsHashChange && this._wantsPushState) {
1896  
1897          // If we've started off with a route from a `pushState`-enabled
1898          // browser, but we're currently in a browser that doesn't support it...
1899          if (!this._hasPushState && !this.atRoot()) {
1900            var rootPath = this.root.slice(0, -1) || '/';
1901            this.location.replace(rootPath + '#' + this.getPath());
1902            // Return immediately as browser will do redirect to new url
1903            return true;
1904  
1905          // Or if we've started out with a hash-based route, but we're currently
1906          // in a browser where it could be `pushState`-based instead...
1907          } else if (this._hasPushState && this.atRoot()) {
1908            this.navigate(this.getHash(), {replace: true});
1909          }
1910  
1911        }
1912  
1913        // Proxy an iframe to handle location events if the browser doesn't
1914        // support the `hashchange` event, HTML5 history, or the user wants
1915        // `hashChange` but not `pushState`.
1916        if (!this._hasHashChange && this._wantsHashChange && !this._usePushState) {
1917          this.iframe = document.createElement('iframe');
1918          this.iframe.src = 'javascript:0';
1919          this.iframe.style.display = 'none';
1920          this.iframe.tabIndex = -1;
1921          var body = document.body;
1922          // Using `appendChild` will throw on IE < 9 if the document is not ready.
1923          var iWindow = body.insertBefore(this.iframe, body.firstChild).contentWindow;
1924          iWindow.document.open();
1925          iWindow.document.close();
1926          iWindow.location.hash = '#' + this.fragment;
1927        }
1928  
1929        // Add a cross-platform `addEventListener` shim for older browsers.
1930        var addEventListener = window.addEventListener || function(eventName, listener) {
1931          return attachEvent('on' + eventName, listener);
1932        };
1933  
1934        // Depending on whether we're using pushState or hashes, and whether
1935        // 'onhashchange' is supported, determine how we check the URL state.
1936        if (this._usePushState) {
1937          addEventListener('popstate', this.checkUrl, false);
1938        } else if (this._useHashChange && !this.iframe) {
1939          addEventListener('hashchange', this.checkUrl, false);
1940        } else if (this._wantsHashChange) {
1941          this._checkUrlInterval = setInterval(this.checkUrl, this.interval);
1942        }
1943  
1944        if (!this.options.silent) return this.loadUrl();
1945      },
1946  
1947      // Disable Backbone.history, perhaps temporarily. Not useful in a real app,
1948      // but possibly useful for unit testing Routers.
1949      stop: function() {
1950        // Add a cross-platform `removeEventListener` shim for older browsers.
1951        var removeEventListener = window.removeEventListener || function(eventName, listener) {
1952          return detachEvent('on' + eventName, listener);
1953        };
1954  
1955        // Remove window listeners.
1956        if (this._usePushState) {
1957          removeEventListener('popstate', this.checkUrl, false);
1958        } else if (this._useHashChange && !this.iframe) {
1959          removeEventListener('hashchange', this.checkUrl, false);
1960        }
1961  
1962        // Clean up the iframe if necessary.
1963        if (this.iframe) {
1964          document.body.removeChild(this.iframe);
1965          this.iframe = null;
1966        }
1967  
1968        // Some environments will throw when clearing an undefined interval.
1969        if (this._checkUrlInterval) clearInterval(this._checkUrlInterval);
1970        History.started = false;
1971      },
1972  
1973      // Add a route to be tested when the fragment changes. Routes added later
1974      // may override previous routes.
1975      route: function(route, callback) {
1976        this.handlers.unshift({route: route, callback: callback});
1977      },
1978  
1979      // Checks the current URL to see if it has changed, and if it has,
1980      // calls `loadUrl`, normalizing across the hidden iframe.
1981      checkUrl: function(e) {
1982        var current = this.getFragment();
1983  
1984        // If the user pressed the back button, the iframe's hash will have
1985        // changed and we should use that for comparison.
1986        if (current === this.fragment && this.iframe) {
1987          current = this.getHash(this.iframe.contentWindow);
1988        }
1989  
1990        if (current === this.fragment) {
1991          if (!this.matchRoot()) return this.notfound();
1992          return false;
1993        }
1994        if (this.iframe) this.navigate(current);
1995        this.loadUrl();
1996      },
1997  
1998      // Attempt to load the current URL fragment. If a route succeeds with a
1999      // match, returns `true`. If no defined routes matches the fragment,
2000      // returns `false`.
2001      loadUrl: function(fragment) {
2002        // If the root doesn't match, no routes can match either.
2003        if (!this.matchRoot()) return this.notfound();
2004        fragment = this.fragment = this.getFragment(fragment);
2005        return _.some(this.handlers, function(handler) {
2006          if (handler.route.test(fragment)) {
2007            handler.callback(fragment);
2008            return true;
2009          }
2010        }) || this.notfound();
2011      },
2012  
2013      // When no route could be matched, this method is called internally to
2014      // trigger the `'notfound'` event. It returns `false` so that it can be used
2015      // in tail position.
2016      notfound: function() {
2017        this.trigger('notfound');
2018        return false;
2019      },
2020  
2021      // Save a fragment into the hash history, or replace the URL state if the
2022      // 'replace' option is passed. You are responsible for properly URL-encoding
2023      // the fragment in advance.
2024      //
2025      // The options object can contain `trigger: true` if you wish to have the
2026      // route callback be fired (not usually desirable), or `replace: true`, if
2027      // you wish to modify the current URL without adding an entry to the history.
2028      navigate: function(fragment, options) {
2029        if (!History.started) return false;
2030        if (!options || options === true) options = {trigger: !!options};
2031  
2032        // Normalize the fragment.
2033        fragment = this.getFragment(fragment || '');
2034  
2035        // Strip trailing slash on the root unless _trailingSlash is true
2036        var rootPath = this.root;
2037        if (!this._trailingSlash && (fragment === '' || fragment.charAt(0) === '?')) {
2038          rootPath = rootPath.slice(0, -1) || '/';
2039        }
2040        var url = rootPath + fragment;
2041  
2042        // Strip the fragment of the query and hash for matching.
2043        fragment = fragment.replace(pathStripper, '');
2044  
2045        // Decode for matching.
2046        var decodedFragment = this.decodeFragment(fragment);
2047  
2048        if (this.fragment === decodedFragment) return;
2049        this.fragment = decodedFragment;
2050  
2051        // If pushState is available, we use it to set the fragment as a real URL.
2052        if (this._usePushState) {
2053          this.history[options.replace ? 'replaceState' : 'pushState']({}, document.title, url);
2054  
2055        // If hash changes haven't been explicitly disabled, update the hash
2056        // fragment to store history.
2057        } else if (this._wantsHashChange) {
2058          this._updateHash(this.location, fragment, options.replace);
2059          if (this.iframe && fragment !== this.getHash(this.iframe.contentWindow)) {
2060            var iWindow = this.iframe.contentWindow;
2061  
2062            // Opening and closing the iframe tricks IE7 and earlier to push a
2063            // history entry on hash-tag change.  When replace is true, we don't
2064            // want this.
2065            if (!options.replace) {
2066              iWindow.document.open();
2067              iWindow.document.close();
2068            }
2069  
2070            this._updateHash(iWindow.location, fragment, options.replace);
2071          }
2072  
2073        // If you've told us that you explicitly don't want fallback hashchange-
2074        // based history, then `navigate` becomes a page refresh.
2075        } else {
2076          return this.location.assign(url);
2077        }
2078        if (options.trigger) return this.loadUrl(fragment);
2079      },
2080  
2081      // Update the hash location, either replacing the current entry, or adding
2082      // a new one to the browser history.
2083      _updateHash: function(location, fragment, replace) {
2084        if (replace) {
2085          var href = location.href.replace(/(javascript:|#).*$/, '');
2086          location.replace(href + '#' + fragment);
2087        } else {
2088          // Some browsers require that `hash` contains a leading #.
2089          location.hash = '#' + fragment;
2090        }
2091      }
2092  
2093    });
2094  
2095    // Create the default Backbone.history.
2096    Backbone.history = new History;
2097  
2098    // Helpers
2099    // -------
2100  
2101    // Helper function to correctly set up the prototype chain for subclasses.
2102    // Similar to `goog.inherits`, but uses a hash of prototype properties and
2103    // class properties to be extended.
2104    var extend = function(protoProps, staticProps) {
2105      var parent = this;
2106      var child;
2107  
2108      // The constructor function for the new subclass is either defined by you
2109      // (the "constructor" property in your `extend` definition), or defaulted
2110      // by us to simply call the parent constructor.
2111      if (protoProps && _.has(protoProps, 'constructor')) {
2112        child = protoProps.constructor;
2113      } else {
2114        child = function(){ return parent.apply(this, arguments); };
2115      }
2116  
2117      // Add static properties to the constructor function, if supplied.
2118      _.extend(child, parent, staticProps);
2119  
2120      // Set the prototype chain to inherit from `parent`, without calling
2121      // `parent`'s constructor function and add the prototype properties.
2122      child.prototype = _.create(parent.prototype, protoProps);
2123      child.prototype.constructor = child;
2124  
2125      // Set a convenience property in case the parent's prototype is needed
2126      // later.
2127      child.__super__ = parent.prototype;
2128  
2129      return child;
2130    };
2131  
2132    // Set up inheritance for the model, collection, router, view and history.
2133    Model.extend = Collection.extend = Router.extend = View.extend = History.extend = extend;
2134  
2135    // Throw an error when a URL is needed, and none is supplied.
2136    var urlError = function() {
2137      throw new Error('A "url" property or function must be specified');
2138    };
2139  
2140    // Wrap an optional error callback with a fallback error event.
2141    var wrapError = function(model, options) {
2142      var error = options.error;
2143      options.error = function(resp) {
2144        if (error) error.call(options.context, model, resp, options);
2145        model.trigger('error', model, resp, options);
2146      };
2147    };
2148  
2149    // Provide useful information when things go wrong. This method is not meant
2150    // to be used directly; it merely provides the necessary introspection for the
2151    // external `debugInfo` function.
2152    Backbone._debug = function() {
2153      return {root: root, _: _};
2154    };
2155  
2156    return Backbone;
2157  });