https://www.uab.edu/joomla4/media/templates/site/sleepyDragon/js/scripts.js

1/**
2 * sleepyDragon template scripts
3 * -----------------------------
4 * Back to Top (accessible)
5 */
6(function () {
7  'use strict';
8
9  const backToTop = document.querySelector('.back-to-top');
10  if (!backToTop) return;
11
12  const OFFSET_PX = 220;
13
14  const prefersReducedMotion =
15    window.matchMedia &&
16    window.matchMedia('(prefers-reduced-motion: reduce)').matches;
17
18  if (!backToTop.hasAttribute('aria-label') && !backToTop.getAttribute('aria-labelledby')) {
19    backToTop.setAttribute('aria-label', 'Back to top');
20  }
21
22  const updateBackToTopVisibility = () => {
23    if (window.scrollY > OFFSET_PX) {
24      backToTop.style.display = '';
25      backToTop.classList.add('is-visible');
26    } else {
27      backToTop.classList.remove('is-visible');
28      backToTop.style.display = 'none';
29    }
30  };
31
32  // Initial state + scroll updates
33  updateBackToTopVisibility();
34  window.addEventListener('scroll', updateBackToTopVisibility, { passive: true });
35
36  backToTop.addEventListener('click', (event) => {
37    event.preventDefault();
38
39    const target =
40      document.getElementById('top');
41
42    const focusTarget = () => {
43      if (!target) return;
44
45      if (!target.hasAttribute('tabindex')) {
46        target.setAttribute('tabindex', '-1');
47      }
48
49      try {
50        target.focus({ preventScroll: true });
51      } catch (e) {
52        target.focus();
53      }
54    };
55
56    if (prefersReducedMotion) {
57      window.scrollTo(0, 0);
58      focusTarget();
59      return;
60    }
61
62    window.scrollTo({ top: 0, behavior: 'smooth' });
63
64    const waitForTop = () => {
65      if (window.scrollY <= 1) {
66        focusTarget();
67        return;
68      }
69      requestAnimationFrame(waitForTop);
70    };
71
72    requestAnimationFrame(waitForTop);
73  });
74})();