Deferred object with standard Promise API

deferred-promise-function.js

var event = new Event('build');
window.addEventListener('build', eventHandler, false);

var defer = null;
function eventHandler() {
	console.log('Event received');
	defer.resolve('hello');
}

function Deferred () { // Wrapper to get Deferred object and promise
	var defer = {};

	defer.promise = new Promise (function (resolve, reject) {
		defer.resolve = resolve.bind(this);
		defer.reject = reject.bind(this);
	}); 

	return defer;
}

function click() {
	defer = new Deferred(); // Create new promise and get deferred object
	return defer.promise; // But returns the promise
}

click().then(data => console.log('Click completed', data));
window.dispatchEvent(event);

deferred-promise-handmade.js

var resolvePromise = null; 

// Async event the click is waiting for
var event = new Event('build');
window.addEventListener('build', eventHandler, false);

function eventHandler() {
	console.log('Event received');
  	resolvePromise('hello');
}

function click() {
	return new Promise (function (resolve, reject) {
    	// Default API doesn't allow to get a deferred object
    	// No choice but to export the resolve function
		resolvePromise = resolve.bind(this);
	});
}

// Complete click once the event is received
click().then(data => console.log('Click completed', data));

// Triggers async event for click to resolve the promise
window.dispatchEvent(event);