https://www.fullfabric.com/js/navbar-scroll.js

1(function() {
2  var navbar = document.querySelector('.navbar');
3  if (!navbar) return;
4  var threshold = 10;
5  var wasTransparent = navbar.classList.contains('is-transparent');
6  function onScroll() {
7    if (window.scrollY > threshold) {
8      navbar.classList.add('is-scrolled');
9      if (wasTransparent) {
10        navbar.classList.remove('is-transparent');
11      }
12    } else {
13      navbar.classList.remove('is-scrolled');
14      if (wasTransparent) {
15        navbar.classList.add('is-transparent');
16      }
17    }
18  }
19  window.addEventListener('scroll', onScroll, { passive: true });
20  onScroll();
21})();