(function() { var prevScrollpos = window.pageYOffset; window.addEventListener('scroll', function() { var header = document.getElementById("scrolling-header"); if (!header) { return; } var currentScrollPos = window.pageYOffset; if (prevScrollpos > currentScrollPos) { header.style.top = "0"; } else { header.style.top = "-100px"; } prevScrollpos = currentScrollPos; }); })();