How to fire only once Mousewheel scroll

Question

I am trying on scroll with mousewheel to do some actions. I want no matter how fast or how many times you scroll the wheel, it to count as "one". Now if you scroll fast it will count more times.

https://stackblitz.com/edit/angular-yttk3y

Answer 1

Have a timer to restrict the scroll for certain duration and retain the scroll direction to detect change in scroll direction.

import { Directive, HostListener } from '@angular/core';
import { timer } from 'rxjs';
@Directive({
  selector: '[appMouseScroll]'
})
export class MouseScrollDirective {
  Ttimer;
  isMouseWheelInRogress;
  scrollUp;

  @HostListener('wheel', ['$event']) onMouseScroll(e) {

    if (!this.isMouseWheelInRogress || (!this.scrollUp && e.deltaY < 0 || this.scrollUp && e.deltaY > 0)) {
      if (this.Ttimer) {
        this.Ttimer.unsubscribe();
      }
      this.Ttimer = timer(500).subscribe(() => {
        this.isMouseWheelInRogress = false;
      });

      if (e.deltaY < 0) {
        this.scrollUp = true;
        console.log('scrolling up');
      } else if (e.deltaY > 0) {
        this.scrollUp = false;
        console.log('scrolling down');
      }
    }
    this.isMouseWheelInRogress = true;
  }
}