View source for Emitter in Node

[[Category:Node.js]]
== Sample Code ==
<pre class="brush:js;">
const EventEmitter = require('events');
const emitter = new EventEmitter();

//Register a listener 
emitter.on('messageLogged', function(){
   console.log('Listener called');
});

// Raise an event 
emitter.emit('messageLogged');

</pre>

Registration must come before raising

=== Event Arguments ===
<pre class="brush:js;">
emitter.on('messageLogged', function(arg){
   console.log('Listener called', arg);
});

emitter.emit('messageLogged', {id:1, url:'http://...'});
</pre>
 
==== Arrow Function ====
<pre class="brush:js;">
emitter.on('messageLogged',(arg) => {
   console.log('Listener called', arg);
});

emitter.emit('messageLogged', {id:1, url:'http://...'});
</pre>
== Using in a Class ==
=== Logger.js ===
<pre class="brush:js;">
const EventEmitter = require('events');
class Logger extends EventEmitter {

  log(message){
     console.log(message);
     this.emit('messageLogged', {id:1, url:http://'});
  }
};

module.exports = Logger;
</pre>

=== App.js ===
<pre class="brush:js;">
const EventEmitter = require('events');
const Logger = require('./logger');
const logger = new Logger();

//Register a listener 
logger.on('messageLogged', (arg) => {
   console.log('Listener called', arg);
});
logger.log('message');
</pre>