web/_javascript/commons/topbar-switch.js

/*
 * Hide Header on scroll down
 */

$(function() {

  const topbarWrapper = $("#topbar-wrapper");
  const toc = $("#toc-wrapper");
  const access = $(".access");
  const searchInput = $("#search-input");

  let didScroll;
  let lastScrollTop = 0;

  const delta = 5;
  const topbarHeight = topbarWrapper.outerHeight();

  function hasScrolled() {
    var st = $(this).scrollTop();

    /* Make sure they scroll more than delta */
    if (Math.abs(lastScrollTop - st) <= delta) {
      return;
    }

    if (st > lastScrollTop && st > topbarHeight) {
      /* Scroll Down */
      topbarWrapper.removeClass("topbar-down").addClass("topbar-up");

      if (toc.length > 0) {
        toc.removeClass("topbar-down");
      }

      if (access.length > 0) {
        access.removeClass("topbar-down");
      }

      if (searchInput.is(":focus")) {
        searchInput.blur(); /* remove focus */
      }

    } else if (st + $(window).height() < $(document).height()) {
      /* Scroll Up */
      topbarWrapper.removeClass("topbar-up").addClass("topbar-down");
      if (toc.length > 0) {
        toc.addClass("topbar-down");
      }
      if (access.length > 0) {
        access.addClass("topbar-down");
      }
    }

    lastScrollTop = st;
  }

  $(window).scroll(function(event) {
    if ($("#topbar-title").is(":hidden")) { /* Not in small screens */
      didScroll = true;
    }
  });

  setInterval(function() {
    if (didScroll) {
      hasScrolled();
      didScroll = false;
    }
  }, 250);

});