rxjs里delay operators的用法

Delays the emission of items from the source Observable by a given timeout or until a given Date.

例子：

const clicks = fromEvent(document, 'click');
    const delayedClicks = clicks.pipe(delay(1000)); // each click emitted after 1 second
    clicks.subscribe(x => console.log('diablo normal: ' + x));
    delayedClicks.subscribe(x => console.log('diablo delayed: ' + x));

测试结果：

delayed Observable emit value的时间戳总是比normal Observable晚一秒钟。