Function returning the same promise as long it's not fullfilled/rejected.

index.js

function getSomething() {
	/**
	 * Returns a promise that fullfills in 15 seconds
	 **/
	if (getSomething._promise) {
		return getSomething._promise;
	} else {
		return getSomething._promise = new Promise(function(resolve, reject) {
			setTimeout(function() {
				getSomething._promise = null;
				resolve('something');
			}, 15000);
		});
	}
}

/*
Running getSomething more than once before its fullfilment returns the same promise. 
Useful if you don't want to run a XHR call more than once.
*/
var p1 = getSomething();
var p2 = getSomething();
/* p1 === p2 */