Node.js EventEmitter.removeListener() 方法详解

Node.js中events.emitter.removeListener方法使用说明

方法概述：

删除特定事件对应的指定监听函数。

语法格式：

emitter.removeListener(event, listener)

参数说明：

event (string) 事件名称

listener (function) 先前注册的监听函数

示例演示：

var callback = function(stream) {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

底层源码：

// 仅当监听器被移除时触发 'removeListener' 事件
EventEmitter.prototype.removeListener = function(type, listener) {
var list, position, length, i;
if (!util.isFunction(listener))
throw TypeError('listener must be a function');
if (!this._events || !this._events[type])
return this;
list = this._events[type];
length = list.length;
position = -1;
if (list === listener ||
(util.isFunction(list.listener) && list.listener === listener)) {
delete this._events[type];
if (this._events.removeListener)
this.emit('removeListener', type, listener);
} else if (util.isObject(list)) {
for (i = length; i-- > 0;) {
if (list[i] === listener ||
(list[i].listener && list[i].listener === listener)) {
position = i;
break;
      }
    }
if (position < 0)
return this;
if (list.length === 1) {
list.length = 0;
delete this._events[type];
} else {
list.splice(position, 1);
    }
if (this._events.removeListener)
this.emit('removeListener', type, listener);
  }
return this;
};