用了backbone一段时间了,做一些笔记和总结,看的源码是1.12
backbone有events,model,collection,histoty,router,view这些模块,其中events是最基础的,其他的模块的prototype全部都扩展了他,所以events是非常重要的,真的很重要,还好代码比较简单,也比较好理解
这个里面的代码是从backbone里面剥离出来,然后一点一点研究和调试出来的,可以单独运行,依赖underscore
1 (function(){ 2 this.Backbone = {}; 3 var array = []; 4 var slice = array.slice; 5 // Regular expression used to split event strings. 6 //劈开eventsApi函数里面传入name,如果name是带空格的字符串 7 var eventSplitter = /\s+/; 8 9 // Implement fancy features of the Events API such as multiple event 10 // names `"change blur"` and jQuery-style event maps `{change: action}` 11 // in terms of the existing API. 12 //如果传入的name(这个对应绑定 删除 触发 监听的事件名)为obj 或者是带空格的字符串，则批量进行相关的操作 13 var eventsApi = function(obj, action, name, rest) { 14 if (!name) return true; 15 16 // Handle event maps. 17 if (typeof name === 'object') { 18 for (var key in name) { 19 obj[action].apply(obj, [key, name[key]].concat(rest)); 20 } 21 return false; 22 } 23 24 // Handle space separated event names. 25 if (eventSplitter.test(name)) { 26 var names = name.split(eventSplitter); 27 for (var i = 0, length = names.length; i < length; i++) { 28 obj[action].apply(obj, [names[i]].concat(rest)); 29 } 30 return false; 31 } 32 33 return true; 34 }; 35 36 37 38 var Events = Backbone.Events = { 39 // Bind an event to a `callback` function. Passing `"all"` will bind 40 // the callback to all events fired. 41 // 参数的传入为 事件名, 回调, 回调里面this指向的对象 42 on: function(name, callback, context) { 43 if (!eventsApi(this, 'on', name, [callback, context]) || !callback) return this; 44 //对象内部生成一个_events对象 key对应事件名, value为一个数组,里面添加相关的回调函数 45 this._events || (this._events = {}); 46 var events = this._events[name] || (this._events[name] = []); 47 //第3个和第4个参数,表示回调函数触发的是偶, 函数里面this的指向 48 events.push({callback: callback, context: context, ctx: context || this}); 49 return this; 50 }, 51 // Bind an event to only be triggered a single time. After the first time 52 // the callback is invoked, it will be removed. 53 // 跟on一样的入参 ,他只会执行一次 54 once: function(name, callback, context) { 55 if (!eventsApi(this, 'once', name, [callback, context]) || !callback) return this; 56 var self = this; 57 //真正绑定进_.events的事故once 而不是callback，当once执行完一次后,就从_events上面删除掉了 58 var once = _.once(function() { 59 self.off(name, once); 60 callback.apply(this, arguments); 61 }); 62 once._callback = callback; 63 return this.on(name, once, context); 64 }, 65 66 // Trigger one or many events, firing all bound callbacks. Callbacks are 67 // passed the same arguments as `trigger` is, apart from the event name 68 // (unless you're listening on `"all"`, which will cause your callback to 69 // receive the true name of the event as the first argument). 70 trigger: function(name) { 71 if (!this._events) return this; 72 var args = slice.call(arguments, 1); 73 if (!eventsApi(this, 'trigger', name, args)) return this; 74 var events = this._events[name]; 75 var allEvents = this._events.all; 76 //通过name 找到对应的回调数组 依次执行里面的回调 77 if (events) triggerEvents(events, args); 78 //查看是否绑定了all事件 如果绑定也会出阿发 79 if (allEvents) triggerEvents(allEvents, arguments); 80 return this; 81 }, 82 83 // Remove one or many callbacks. If `context` is null, removes all 84 // callbacks with that function. If `callback` is null, removes all 85 // callbacks for the event. If `name` is null, removes all bound 86 // callbacks for all events. 87 off: function(name, callback, context) { 88 if (!this._events || !eventsApi(this, 'off', name, [callback, context])) return this; 89 90 // Remove all callbacks for all events. 91 //如果参数不存在 就移除所有的事件 92 if (!name && !callback && !context) { 93 this._events = void 0; 94 return this; 95 } 96 97 var names = name ? [name] : _.keys(this._events); 98 for (var i = 0, length = names.length; i < length; i++) { 99 name = names[i]; 100 101 // Bail out if there are no events stored. 102 var events = this._events[name]; 103 if (!events) continue; 104 105 // Remove all callbacks for this event. 106 //如果只传递name这一个参数 就删除name对应的整个数组 107 if (!callback && !context) { 108 delete this._events[name]; 109 continue; 110 } 111 112 // Find any remaining events. 113 // 114 //如果如果传递了第2个参数 只删除_events[name]里面对应的callback 115 //如果传递了第2个参数,第3个参数,还要判断_events[name]里面的callback是否等于第2个参数,context是否等于第3个参数 116 //把那么不符合条件的用remaining保存起来 117 //然后用this._events[name] = remaining替换掉之前的 118 var remaining = []; 119 for (var j = 0, k = events.length; j < k; j++) { 120 var event = events[j]; 121 if ( 122 callback && callback !== event.callback && 123 callback !== event.callback._callback || 124 context && context !== event.context 125 ) { 126 remaining.push(event); 127 } 128 } 129 130 // Replace events if there are any remaining. Otherwise, clean up. 131 if (remaining.length) { 132 this._events[name] = remaining; 133 } else { 134 delete this._events[name]; 135 } 136 } 137 138 return this; 139 }, 140 // Tell this object to stop listening to either specific events ... or 141 // to every object it's currently listening to. 142 stopListening: function(obj, name, callback) { 143 var listeningTo = this._listeningTo; 144 if (!listeningTo) return this; 145 var remove = !name && !callback; 146 if (!callback && typeof name === 'object') callback = this; 147 if (obj) (listeningTo = {})[obj._listenId] = obj; 148 for (var id in listeningTo) { 149 obj = listeningTo[id]; 150 obj.off(name, callback, this); 151 if (remove || _.isEmpty(obj._events)) delete this._listeningTo[id]; 152 } 153 return this; 154 } 155 } 156 157 var listenMethods = {listenTo: 'on', listenToOnce: 'once'}; 158 159 // Inversion-of-control versions of `on` and `once`. Tell *this* object to 160 // listen to an event in another object ... keeping track of what it's 161 // listening to. 162 // on listenTo 163 _.each(listenMethods, function(implementation, method) { 164 Events[method] = function(obj, name, callback) { 165 //obj 为被监听的对象 166 //name 为被监听的事件名 167 // callback 是obj触发了name事件后, 别监听到了 然后执行的回调 168 var listeningTo = this._listeningTo || (this._listeningTo = {}); 169 var id = obj._listenId || (obj._listenId = _.uniqueId('l')); 170 //给监听对象添加一个_listeningTo的属性 它的值是一个对象key为_listenId value为被监听的对象 171 //被监听对象添加一个_listenId的属性 它的值为_listenId 172 listeningTo[id] = obj; 173 174 if (!callback && typeof name === 'object') callback = this; 175 obj[implementation](name, callback, this); 176 return this; 177 }; 178 }); 179 180 // A difficult-to-believe, but optimized internal dispatch function for 181 // triggering events. Tries to keep the usual cases speedy (most internal 182 // Backbone events have 3 arguments). 183 //批量处理_events里面的回调事件的东西 184 //参数小于等于3个用call 大于3个用apply 为毛会这样 185 var triggerEvents = function(events, args) { 186 var ev, i = -1, l = events.length, a1 = args[0], a2 = args[1], a3 = args[2]; 187 switch (args.length) { 188 case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx); return; 189 case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1); return; 190 case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2); return; 191 case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2, a3); return; 192 default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args); return; 193 } 194 }; 195 })();