SOURCE

function getYear() {
	return new Promise((reslove, reject) => {
    setTimeout(_ => reslove(2018), 1000)
  })
}

function getBirth() {
  return new Promise((reslove, reject) => {
    setTimeout(_ => reslove(1993), 3000)
  })
}

const getYear$ = Rx.Observable.fromPromise(getYear());
const getBirth$ = Rx.Observable.fromPromise(getBirth());

getYear$.combineLatest(getBirth$, (y, b) => y-b)
				.subscribe(v => console.info("年龄", v))

<button id="getAge">快点吧</button>