方法说明：

移除所有监听器，如果指定event，则将移除指定事件的所有监听器。

语法：

emitter.removeAllListeners([event])

接收参数：

event 事件类型，支持多个

例子：

//移除所有监听器

 

emitter.removeAllListeners()

 

//移除指定event的所有监听器

 

emitter.removeAllListeners('data')

源码：

EventEmitter.prototype.removeAllListeners = function(type) {

  var key, listeners;

  if (!this._events)

    return this;

  // not listening for removeListener, no need to emit

  if (!this._events.removeListener) {

    if (arguments.length === 0)

      this._events = {};

    else if (this._events[type])

      delete this._events[type];

    return this;

  }

  // emit removeListener for all listeners on all events

  if (arguments.length === 0) {

    for (key in this._events) {

      if (key === 'removeListener') continue;

      this.removeAllListeners(key);

    }

    this.removeAllListeners('removeListener');

    this._events = {};

    return this;

  }

  listeners = this._events[type];

  if (util.isFunction(listeners)) {

    this.removeListener(type, listeners);

  } else {

    // LIFO order

    while (listeners.length)

      this.removeListener(type, listeners[listeners.length - 1]);

  }

  delete this._events[type];

  return this;

};