Emitter in Node

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');

Registration must come before raising

Event Arguments

emitter.on('messageLogged', function(arg){
   console.log('Listener called', arg);
});

emitter.emit('messageLogged', {id:1, url:'http://...'});

Arrow Function

emitter.on('messageLogged',(arg) => {
   console.log('Listener called', arg);
});

emitter.emit('messageLogged', {id:1, url:'http://...'});