sass-site/source/assets/js/components/navigation.ts

// Documentation Nav Scroll
$(function () {
  // Vars
  const nav = $('.sl-c-list-navigation-wrapper');
  const sticky = nav.offset();

  // Added sticky class when window top is great than nav top
  const stickyNav = () => {
    if (
      nav.length > 0 &&
      sticky &&
      ($(window).scrollTop() ?? 0) >= sticky.top
    ) {
      $('.sl-l-medium-holy-grail__body').addClass('sl-js-nav--is-sticky');
    } else {
      $('.sl-l-medium-holy-grail__body').removeClass('sl-js-nav--is-sticky');
    }
  };

  // When scrolling the page, execute stickyNav
  $(window).on('scroll', function () {
    stickyNav();
  });

  return stickyNav();
});