javascript - 重新订阅 takeUntil/skipUntil

Question

以下代码定义了我想要的行为(有效)。仅当鼠标按下时才会触发 mousemove 事件。

Rx.Observable.fromEvent(window,"mouseup")
.subscribe( 
  () => {
      if(subscription)
         subscription.dispose();
  }
) 

Rx.Observable.fromEvent(window,"mousedown")
.subscribe(
  () => {
      subscription = Rx.Observable.fromEvent(window,"mousemove")
                     .subscribe(
                       (event) => console.log(event)
                     )
  }
) 

我想使用 takeUntil/skipUntil 运算符重写它。但这失败了:

let fs =  [
  (e) => console.log(e),
  (err) => console.log(err),
  () => {
      console.log('done')  
      source.subscribe(...fs);
  }
 ];

let getDown = () => Rx.Observable.fromEvent(document,"mousedown");
let getUp = () => Rx.Observable.fromEvent(document,"mouseup");

let source = Rx.Observable.fromEvent(document,"mousemove")
.skipUntil(getDown())
.takeUntil(getUp());

source.subscribe(
   ...fs
)

我该怎么做？谢谢!

Answer 1

这个问题通常通过将触发流的每个元素投影到所需的源流然后将其展平(通常使用 switchMap 来实现)来解决。在这种情况下，您希望将下跌预测为上涨。像这样:

const source = getDown().switchMap(() => Rx.Observable.fromEvent(document, "mousemove").takeUntil(getUp());