onScroll.js

function onScroll(callbackDown, callbackUp) {
  let lastScrollTop = 0;
  let scrollDownLock = false;
  let scrollUpLock = false;
  let lockProcess = false;
  let isScrolling = null;
  let tl;

  return function () {
    window.clearTimeout(isScrolling);
    isScrolling = setTimeout(() => run(), 66);
  }

  function run() {
    let scrollTop = window.pageYOffset || document.documentElement.scrollTop;

    if (lockProcess === false) {
      if (scrollTop > (lastScrollTop + 50) && scrollDownLock === false) {
        scrollDownLock = true;
        scrollUpLock = false;
        lockProcess = true;
        tl = callbackDown();
      }
      else if (scrollTop < (lastScrollTop - 50) && scrollUpLock === false) {
        scrollUpLock = true;
        scrollDownLock = false;
        lockProcess = true;
        tl = callbackUp();
      }
    }

    lastScrollTop = scrollTop <= 0 ? 0 : scrollTop;

    if (tl && lockProcess) {
      tl.add(() => lockProcess = false)
    }
  }
}