var Events = Backbone.Events = {
// Bind an event to a `callback` function. Passing `"all"` will bind
// the callback to all events fired.
//上面的话就是说如果传递的事件名称是all的话，就会激活所有绑定在上下文上面的事件
on: function(name, callback, context) {
if (!eventsApi(this, 'on', name, [callback, context]) || !callback)
return this;
//当通过正则匹配不到，就要建立一个事件对象，把传递进来的事件对象名称保存
//如name为“alert的时候” ||或运算符 检测对象是否有_events属性,没有就新建一个对象
this._events || (this._events = {});
// ||或运算符 this._events[name] 用来检测在该事件名称是否存在数组对象，如果没有那么就新建一个数组对象
var events = this._events[name] || (this._events[name] = []);
//把新执行的函数体添加到数组里面
/****
callback：回调函数，用来具体的执行函数
ctx:上下文 ||预算符其实就是用来初始化处理的context||this，
如果没有传递上下文对象那么就是默认为this，而在javascript中我们知道this
是当前执行本函数的对象在这个里面就是调用on函数的对象
context:上下文
***/
events.push({callback: callback, context: context, ctx: context || this});
//返回当前对象
return this;
},
// Bind an event to only be triggered a single time. After the first time
// the callback is invoked, it will be removed.
once: function(name, callback, context) {
if (!eventsApi(this, 'once', name, [callback, context]) || !callback) return this;
var self = this;
//_为underscore的别称
var once = _.once(function() {
self.off(name, once);
callback.apply(this, arguments);
});
once._callback = callback;
//最终调用的是on方法
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.
//事件解绑
off: function(name, callback, context) {
//key 编码改善，使用的变量在方法前面声明
var retain, ev, events, names, i, l, j, k;
//如果没有事件绑定或者通过正则规则匹配那么就可以直接返回，
//具体可以看eventsApi的方法分析
if (!this._events || !eventsApi(this, 'off', name, [callback, context])) return this;
if (!name && !callback && !context) {
this._events = {};
return this;
}
//
names = name ? [name] : _.keys(this._events);
for (i = 0, l = names.length; i < l; i++) {
name = names[i];
if (events = this._events[name]) {
this._events[name] = retain = [];
if (callback || context) {
for (j = 0, k = events.length; j < k; j++) {
ev = events[j];
if ((callback && callback !== ev.callback && callback !== ev.callback._callback) ||
(context && context !== ev.context)) {
retain.push(ev);
}
}
}
if (!retain.length)
//关键点，删除事件
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).
//手动执行指定的事件
trigger: function(name) {
if (!this._events) return this;
//如果传递多个参数，那么拆分参数作为入参
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.
//停止事件监听，核心是调用off
stopListening: function(obj, name, callback) {
var listeningTo = this._listeningTo;
if (!listeningTo) return this;
var remove = !name && !callback;
if (!callback && typeof name === 'object') callback = this;
if (obj) (listeningTo = {})[obj._listenId] = obj;
for (var id in listeningTo) {
obj = listeningTo[id];
obj.off(name, callback, this);
if (remove || _.isEmpty(obj._events))
//
delete this._listeningTo[id];
}
return this;
}
};
// Regular expression used to split event strings.
var eventSplitter = /\s+/;//定义事件分割的正则表达式默认是空格
// 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.
//事件分割的api，类jquery风格
/***
@param obj 对象
@param action 事件对象的值包含，on,once,off,trigger等
@param name 事件的名称{}
@param rest 包含回调以及上下文 eventsApi(this, 'on', name, [callback, context])
***/
var eventsApi = function(obj, action, name, rest) {
if (!name) return true;
// Handle event maps.
//name如果是一个map对象就是key-value形式
if (typeof name === 'object') {
for (var key in name) {
//通过分析name对象，连接传递进来的参数作为调用对象的属性
obj[action].apply(obj, [key, name[key]].concat(rest));
}
return false;
}
// Handle space separated event names.name如果不是key-value形式的但是满足正则规则
if (eventSplitter.test(name)) {
//利用正则拆分成为一个数组
var names = name.split(eventSplitter);
//加入对象
for (var i = 0, l = names.length; i < l; i++) {
obj[action].apply(obj, [names[i]].concat(rest));
}
return false;
}
/***
不满足的正则规则的
例如：
object.on("alert",function(){});
例子中alert就是我们所取到的name
***/
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).
//特殊情况激活事件的处理，用来激活所有的事件的时候使用
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.
_.each(listenMethods, function(implementation, method) {
Events[method] = function(obj, name, callback) {
var listeningTo = this._listeningTo || (this._listeningTo = {});
var id = obj._listenId || (obj._listenId = _.uniqueId('l'));
listeningTo[id] = obj;
if (!callback && typeof name === 'object') callback = this;
obj[implementation](name, callback, this);
return this;
};
});
// Aliases for backwards compatibility.别名
Events.bind = Events.on;
Events.unbind = Events.off;
// Allow the `Backbone` object to serve as a global event bus, for folks who
// want global "pubsub" in a convenient place.
//给所有的Backbone对象赋予事件对象的属性
_.extend(Backbone, Events);
?