Scroll to reveal/hide header - JS

window.addEventListener ('DOMContentLoaded', ()=> {


    const   body = document.body,
            scrollUp = "scroll-up",
            scrollDown = "scroll-down";
    let     lastScroll = 0;


    //check for scrol action

    window.addEventListener ('scroll', ()=> {




        //hide and reveal header

            const currentScroll = window.pageYOffset;
              if (currentScroll <= 200) {
                body.classList.remove(scrollUp);
                return;
              }

              if (currentScroll > lastScroll && !body.classList.contains(scrollDown)) {
                // down
                body.classList.remove(scrollUp);
                body.classList.add(scrollDown);

              } else if (
                currentScroll < lastScroll &&
                body.classList.contains(scrollDown)
              ) {
                // up
                body.classList.remove(scrollDown);
                body.classList.add(scrollUp);

              }
              lastScroll = currentScroll;




    })
    // end scroll action



});