How to know when finished working takeUntil

Question

I need to do the last action when "takeUntil" worked and then send that data further, but I can't know exactly when takeUntil finished work. Thanks to all.

  ngOnInit(): void {
    const thumb = document.getElementById("thumb");
    const track: HTMLElement = document.getElementById("track");
    const activeTrack = document.getElementById("active-track");
    const mouseUp = fromEvent(document, "mouseup");

    const mouseMove = fromEvent(document, "mousemove").pipe(
      map((item) => this.mouseEventToCoordinate(item, track))
    );
    const activeTrackClick = fromEvent(activeTrack, "click").pipe(
      map((item) => this.mouseEventToCoordinate(item, track))
    );
    const trackClick = fromEvent(track, "click").pipe(
      map((item) => this.mouseEventToCoordinate(item, track))
    );
    const mouseDown = fromEvent(thumb, "mousedown");

    mouseDown
      .pipe(
        switchMap(() => mouseMove),
        merge(trackClick, activeTrackClick),
        takeUntil(mouseUp),
        repeat()
      )
      .subscribe((item: { trackWidth: number; position: number }) => {
        const newX = (item.position / item.trackWidth) * 100;
        activeTrack.style.width = (newX + 1).toString() + "%";
        thumb.style.left = newX.toString() + "%";

        if (item === "Done") {
          // Do somethings
        }
      });  
    }

Answer 1

takeUntil completes the source Observable up until that. This means that we can utilize completion. repeat starts again completed Observable. So we can do something like so:

mouseDown
  .pipe(
    switchMap(() => mouseMove),
    merge(trackClick, activeTrackClick),
    takeUntil(mouseUp),
    tap({ complete: () => doSomething() }), // This will execute when mouseUp emits and takeUntil completes source Observable
    repeat(),
  )
...