nodejs eventEmitter源码解读

1:添加回调

在看http.createServer(代码模块的时候看到 this.addListener('request', requestListener);代码不太了解看了下下eventEmiter的源码！

emitter.on(event, listener)    

    alias for emitter.addListener(..

emitter.addListener(event, listener)    {

...

if (!this._events[type])
	// Optimize the case of one listener. Don't need the extra array object.
	this._events[type]= listener;
	else if (util.isObject(this._events[type]))
	// If we've already got an array, just append.
	this._events[type].push(listener);
	else
	// Adding the second element, need to change to array.
	this._events[type]= [this._events[type], listener];

...

 （1 如果type类型的event未定义 则创建  （2 如果 event是一个数组对象，则将新的listener压入栈  （3  如果不是对象-是function类型，则创建一个对象，其中初始化时有两个listener function