eventemitter4/doc/examples/1-on.js

EventEmitter4 is an alternative to node's built-in EventEmitter class, and to the existing alternatives EventEmitter2 and EventEmitter3

var EventEmitter=require('../../index.js');
var emitter=new EventEmitter();

emitter.on('finished-eating',function(who) {
        console.log('clean up the table, '+who+'.');
});

emitter.emit('finished-eating','John');