gistfile1.js

/* Consumer.js */
var Consumer = function() {};
Consumer.prototype = {
  findById: function(id) {
    ... some code ...
    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);
}).findById("50ac3d1281abba5454000001");

/* ERROR CODE */
{"code":"InternalError","message":"Object [object Object] has no method 'findById'"}