EventEmitter in composition way.

comp.js

'use strict';
var EventEmitter = require('events').EventEmitter;

var bot = {
    sayHi: function(name) {
        console.log('hi ' + name);
    },
    emitter: new EventEmitter()
};

bot.emitter.on('hello', function(name) {
    console.log('hello ' + name);
});

bot.sayHi('John');
bot.emitter.emit('hello', 'John');