scrollDirection.js

(function() {
  let lastScrollTop = 0;
  let scrollUpEvent = new Event("scrollUp");
  let scrollDownEvent = new Event("scrollDown");

  document.addEventListener("scroll", function(){ // or window.addEventListener("scroll"....
     let scrollTop = window.pageYOffset || document.documentElement.scrollTop;
     if (scrollTop > lastScrollTop){
      document.dispatchEvent(scrollDownEvent);
     } else {
      document.dispatchEvent(scrollUpEvent);
     }
     lastScrollTop = scrollTop;
  }, false);
})