Instructions on the use of the events.emb. once method in node.js

Method description:

Registers a single listener for the specified event, so that the listener fires only once at most, and is immediately unfired.

Grammar:

emitter.once(event, listener)

Receiving parameters:

Event                      (string)                         The event type

Listener                (function)                 The callback function when an event is triggered

Example:

server.once('connection', function (stream) {

  console.log('Ah, we have our first user!');

});

Source:

EventEmitter.prototype.once = function(type, listener) {

  if (!util.isFunction(listener))

    throw TypeError('listener must be a function');

  function g() {

    this.removeListener(type, g);

    listener.apply(this, arguments);

  }

  g.listener = listener;

  this.on(type, g);

  return this;

};