Nodejs Events Demo

nodejs_events_demo.js

var events = require('events');
var emitter = new events.EventEmitter();

emitter.once('knock', function(){     //subscribe to the event
  console.log('Who\'s there???');
  });
emitter.on('knock', function(){     //subscribe to the event
  console.log('Leave us in peace, please!!!');
  });

emitter.emit('knock');             //fire the event
emitter.emit('knock');             //fire the event