observable.js

var a = Rx.Observable.fromEvent(document, 'click')
						.flatMapLatest(function () {
							return Rx.Observable.defer(function () {
								return new Promise(function (resolve) {
									setTimeout(function () { resolve('hey'); }, 2000);
								});
							});
						});

var b = a.subscribe(function () { console.log(arguments[0]); });