gistfile1.js

/* Consumer.js */
var Consumer = function() {};
Consumer.prototype.findById = function(id) {
    this.emit('done', this);
};

util.inherits(Consumer, EventEmitter);
module.exports = Consumer;

/* index.js */
var consumer = new Consumer();
consumer.on('done', function(result) {
  console.log(result);
});

consumer.findById("50ac3d1281abba5454000001");