What is the difference between addListener(event, listener) and on(event, listener) method in node.js?

Question

Here i cannot understand what is the basic difference between these two methods.

var events = require('events'); var eventEmitter = new events.EventEmitter();    var listner1 = function listner1() {     console.log('listner1 executed.'); }  var listner2 = function listner2() {     console.log('listner2 executed.');     }  eventEmitter.addListener('connection', listner1);  eventEmitter.on('connection', listner2);  eventEmitter.emit('connection'); 

Answer 1

.on() is exactly the same as .addListener() in the EventEmitter object.

Straight from the EventEmitter source code:

EventEmitter.prototype.on = EventEmitter.prototype.addListener; 

Sleuthing through the GitHub repository, there is this checkin from Jul 3, 2010 that contains the comment: "Experimental: 'on' as alias to 'addListener'".

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Update in 2017: The documentation for EventEmitter.prototype.addListener() now says this:

Alias for emitter.on(eventName, listener).

Answer 2

Yes you can use "removeListener" with with a listener created with "on". Try it.

var events = require('events'); var eventEmitter = new events.EventEmitter();  // listener #1 var listner1 = function listner1() {    console.log('listner1 executed.'); }  // listener #2 var listner2 = function listner2() {   console.log('listner2 executed.'); }  // Bind the connection event with the listner1 function eventEmitter.addListener('connection', listner1);  // Bind the connection event with the listner2 function eventEmitter.on('connection', listner2);  var eventListeners = require('events').EventEmitter.listenerCount(eventEmitter,'connection'); console.log(eventListeners + " Listner(s) listening to connection event");  // Fire the connection event  eventEmitter.emit('connection');  // Remove the binding of listner1 function eventEmitter.removeListener('connection', listner2); console.log("Listner2 will not listen now.");  // Fire the connection event  eventEmitter.emit('connection');  eventListeners = require('events').EventEmitter.listenerCount(eventEmitter,'connection'); console.log(eventListeners + " Listner(s) listening to connection event");  console.log("Program Ended.");