Resolve promise when async action has finished

promise_once.js

var bar = function (data) {
  return setTimeout(function() {
    return 'async data';
  }, 1000);
}

var foo = function () {
  this._promise new Promise(function(resolve, reject) {
      this.once('bar', resolve)
  })
}

var submitFunc = function() {
  foo.then(function() {
    //do some submit stuff
  })
}