 = window.pageYOffset || document.documentElement.scrollTop;
      if (st > lastScrollTop) { // scroll down
        if (st < 250) {
          gttBtn.style.display = "none";
        } else {
          gttBtn.style.display = "block";
        }

        if (st < 45) {
          return null;
        }

        if (navbar.classList.contains('scrolling')) {
          if (!navbar.classList.contains('navbar--hide')) {
            navbar.classList.add('navbar--hide');
          } else if (navbar.classList.contains('