How to listen scroll event for x scroll and y scroll Individually

Question

I want to listen scroll event and handler them by two function for two scroll.

One need a throttleTime() to save resource and the other cannot use throttleTime() because it need trigger immediately and it doesn't cast too much.

Now I add two fromEvent to handle them but question is they will both be fired if scroll event is triggered.

fromEvent(this.vscroll.nativeElement, 'scroll').pipe(throttleTime(200)).subscribe((e) => {
  if (this.timer) {
    clearTimeout(this.timer);
    this.timer = null;
    this.timer = setTimeout(() => {
      this.updateShow();
    }, 201);
  } else {
    this.timer = setTimeout(() => {
      this.updateShow();
    }, 201);
  }
});
fromEvent(this.vscroll.nativeElement, 'scroll').subscribe((e) => {
  (document.body.querySelector('#headerScroll') as HTMLElement).style.marginLeft = -this.vscroll.nativeElement.scrollLeft + 'px';
});

In my component those two function won't happen at the same time, so what should I do to make it only trigger one function and prevent from the other being executed?

user_2504888 · Answer

Create your single function but store the previous X and Y scroll positions so you can see if they've changed between calls:

var scrollY = 0;
var scrollX = 0;
function onScroll(){
  var doc = document.documentElement;
  if(doc.scrollLeft !== scrollX) {
    scrollX = doc.scrollLeft;
    //Put behaviour for X scroll here
    $("p").text("X SCROLLED!");
  }
  if(doc.scrollTop !== scrollY) {
    scrollY = doc.scrollTop;
    //Put behaviour for Y scroll here
    $("p").text("Y SCROLLED!");
  }
}

window.addEventListener('scroll', onScroll);

How to listen scroll event for x scroll and y scroll Individually

1 Answers