https://www.unizar.es/modules/contrib/back_to_top/js/back_to_top.js?v=10.6.16

1/**
2 * @file
3 * Back To Top behaviors.
4 */
5(function ($, Drupal, once, drupalSettings) {
6
7  var frame;
8  var scrollTo = function (to, duration) {
9    var element = document.scrollingElement || document.documentElement,
10      start = element.scrollTop,
11      change = to - start,
12      startTs = performance.now(),
13      easeOutQuart = function (t, b, c, d) {
14	      t /= d;
15	      t--;
16	      return -c * (t * t * t * t - 1) + b;
17      },
18      animateScroll = function (ts) {
19        var currentTime = ts - startTs;
20        element.scrollTop = parseInt(easeOutQuart(currentTime, start, change, duration));
21        if (currentTime < duration) {
22          frame = requestAnimationFrame(animateScroll);
23        } else {
24          element.scrollTop = to;
25        }
26      };
27    requestAnimationFrame(animateScroll);
28  };
29
30  Drupal.behaviors.backtotop = {
31    attach: function (context, settings) {
32      let isMobile = window.matchMedia("only screen and (max-width: 760px)").matches;
33      if (!(settings.back_to_top.back_to_top_prevent_on_mobile && isMobile)) {
34        var exist = $('#backtotop').length;
35        if (exist == 0) {
36          $(once('backtotop', 'body'), context).each(function () {
37            $('body').append("<nav aria-label='" + Drupal.t("Back to top") + "'><button id='backtotop' aria-label='" + Drupal.t("Back to top") + "'>" + settings.back_to_top.back_to_top_button_text + "</button></nav>");
38          });
39        }
40      }
41
42      backToTop();
43      $(document).on("scroll", function() {
44        backToTop();
45      });
46
47      $(once('backtotop', '#backtotop'), context).each(function () {
48        $(this).click(function () {
49          $("html, body").bind("scroll mousedown DOMMouseScroll mousewheel keyup", function () {
50            if (typeof frame !== 'undefined') {
51              window.cancelAnimationFrame(frame);
52            }
53          });
54          speed = settings.back_to_top.back_to_top_speed;
55            if (speed == null) {
56              speed = 1200;
57            }
58          scrollTo(0, speed);
59        });
60      });
61
62      /**
63       * Hide show back to top links.
64       */
65      function backToTop() {
66        if ($(window).scrollTop() > settings.back_to_top.back_to_top_button_trigger) {
67          $('#backtotop').fadeIn();
68        } else {
69          $('#backtotop').fadeOut();
70        }
71      }
72    }
73  };
74})(jQuery, Drupal, once, drupalSettings);