Backbone中的Events对象的主要直接就是实现自定义事件。(熟悉自定义事件的童鞋可以直接忽略此篇了)直接看源码分析：
// A module that can be mixed in to *any object* in order to provide it with // custom events. You may bind with `on` or remove with `off` callback // functions to an event; `trigger`-ing an event fires all callbacks in // succession. // // var object = {}; // _.extend(object, Backbone.Events); // object.on('expand', function(){ alert('expanded'); }); // object.trigger('expand'); // var Events = Backbone.Events = { // Bind an event to a `callback` function. Passing `"all"` will bind // the callback to all events fired. // 绑定事件 name: 事件名 callback：回调函数 context：回调函数执行时的this on: function(name, callback, context) { // 如果是jquery式的事件绑定（'blur change' {blur: .. change: ..}） 或者没有callback 直接返回 if (!eventsApi(this, 'on', name, [callback, context]) || !callback) return this; this._events || (this._events = {}); var events = this._events[name] || (this._events[name] = []); events.push({callback: callback, context: context, ctx: context || this}); return this; }, // Bind an event to only be triggered a single time. After the first time // the callback is invoked, it will be removed. // 确保只是被触发一次 once: function(name, callback, context) { if (!eventsApi(this, 'once', name, [callback, context]) || !callback) return this; var self = this; var once = _.once(function() { self.off(name, once); callback.apply(this, arguments); }); once._callback = callback; return this.on(name, once, context); }, // Remove one or many callbacks. If `context` is null, removes all // callbacks with that function. If `callback` is null, removes all // callbacks for the event. If `name` is null, removes all bound // callbacks for all events. // 移除绑定事件 off: function(name, callback, context) { var retain, ev, events, names, i, l, j, k; if (!this._events || !eventsApi(this, 'off', name, [callback, context])) return this; if (!name && !callback && !context) { this._events = {}; return this; } // 如果有name, 那么就尝试移除指定的事件 否则话就移除所有的事件 names = name ? [name] : _.keys(this._events); for (i = 0, l = names.length; i < l; i++) { name = names[i]; if (events = this._events[name]) { this._events[name] = retain = []; // 如果有callback 或者 context 需要判断是否相同 // 相同则移除 不同的话就不移除 if (callback || context) { for (j = 0, k = events.length; j < k; j++) { ev = events[j]; if ((callback && callback !== ev.callback && callback !== ev.callback._callback) || (context && context !== ev.context)) { retain.push(ev); } } } // 如果没有任何的监听处理程序 就删除 if (!retain.length) delete this._events[name]; } } return this; }, // Trigger one or many events, firing all bound callbacks. Callbacks are // passed the same arguments as `trigger` is, apart from the event name // (unless you're listening on `"all"`, which will cause your callback to // receive the true name of the event as the first argument). // 触发某类事件 name：事件名 后面可以跟其他参数 trigger: function(name) { if (!this._events) return this; var args = slice.call(arguments, 1); if (!eventsApi(this, 'trigger', name, args)) return this; var events = this._events[name]; var allEvents = this._events.all; if (events) triggerEvents(events, args); if (allEvents) triggerEvents(allEvents, arguments); return this; }, // Tell this object to stop listening to either specific events ... or // to every object it's currently listening to. // 停止监听对象obj的执行name的callback事件 stopListening: function(obj, name, callback) { var listeners = this._listeners; if (!listeners) return this; var deleteListener = !name && !callback; if (typeof name === 'object') callback = this; if (obj) (listeners = {})[obj._listenerId] = obj; for (var id in listeners) { listeners[id].off(name, callback, this); if (deleteListener) delete this._listeners[id]; } return this; } }; // Regular expression used to split event strings. var eventSplitter = /\s+/; // Implement fancy features of the Events API such as multiple event // names `"change blur"` and jQuery-style event maps `{change: action}` // in terms of the existing API. // `"change blur"` `{change: action}` 这两种类型的jquery式事件处理 var eventsApi = function(obj, action, name, rest) { if (!name) return true; // Handle event maps. if (typeof name === 'object') { for (var key in name) { obj[action].apply(obj, [key, name[key]].concat(rest)); } return false; } // Handle space separated event names. if (eventSplitter.test(name)) { var names = name.split(eventSplitter); for (var i = 0, l = names.length; i < l; i++) { obj[action].apply(obj, [names[i]].concat(rest)); } return false; } return true; }; // A difficult-to-believe, but optimized internal dispatch function for // triggering events. Tries to keep the usual cases speedy (most internal // Backbone events have 3 arguments). // 方便触发事件时 传给 事件处理函数 的参数问题 var triggerEvents = function(events, args) { var ev, i = -1, l = events.length, a1 = args[0], a2 = args[1], a3 = args[2]; switch (args.length) { case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx); return; case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1); return; case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2); return; case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2, a3); return; default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args); } }; var listenMethods = {listenTo: 'on', listenToOnce: 'once'}; // Inversion-of-control versions of `on` and `once`. Tell *this* object to // listen to an event in another object ... keeping track of what it's // listening to. // 告知当前对象监听另一个对象obj的某个事件 用于跟踪obj的事件 // 也就是当obj的name类型的事件触发的时候，就会执行当前对象 // 追踪的这个callback _.each(listenMethods, function(implementation, method) { Events[method] = function(obj, name, callback) { var listeners = this._listeners || (this._listeners = {}); var id = obj._listenerId || (obj._listenerId = _.uniqueId('l')); listeners[id] = obj; if (typeof name === 'object') callback = this; obj[implementation](name, callback, this); return this; }; }); // Aliases for backwards compatibility. Events.bind = Events.on; Events.unbind = Events.off;
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