ForkJoin并没有像预期的那样工作

Question

为什么这样的代码只打印一个＆＃39; 0＆＃39;？如何让它先打印两个零然后完成？

const example = Rx.Observable.forkJoin(
      Rx.Observable.interval(500).takeWhile((val) => {
                console.log(val);
                return false;}).takeUntil(Rx.Observable.timer(30000)),
      Rx.Observable.interval(500).takeWhile((val) => {
                console.log(val);
                return  false;}).takeUntil(Rx.Observable.timer(30000))
    );
    const subscribe = example.subscribe(val => console.log(val));

jsFiddle