Events in the node. Js. EventEmitter. ListenerCount method instructions

Method description:

Returns the number of listeners registered for the specified event.

Grammar:

EventEmitter.listenerCount(emitter, event)

Receiving parameters:

Emitter                        Event transmitter
Event                              The event

Example:

if(events.EventEmitter.listenerCount(this, 'feedback') == 0) {

    //....

}

Source:

EventEmitter.listenerCount = function(emitter, type) {

  var ret;

  if (!emitter._events || !emitter._events[type])

    ret = 0;

  else if (util.isFunction(emitter._events[type]))

    ret = 1;

  else

    ret = emitter._events[type].length;

  return ret;

};