eventpromise.js

var EventEmitter = require("events").EventEmitter

var events = new EventEmitter()

var deferred = Promise.defer();

events.once("ready", function() {
  console.log("events once callback")
  deferred.resolve("how amazing")
})

console.log("waiting 3 seconds");
setTimeout(function() {
  events.emit("ready")
}, 3000)

module.exports = {
  ready: deferred.promise
}

index.js

var p = require('./eventpromise.js')

p.ready.then(function(res) {
  console.log('promise then fired', res)
}).catch(function(err) {
  console.error('promise catch fired')
})