https://www.metalocus.es/themes/custom/paltana/components/01_atoms/back_to_top/back_to_top.js?tm7z3o

1(function (Drupal) {
2  Drupal.behaviors.back_to_top = {
3    attach: function attach(context) {
4      const back_to_tops = once('backToTop', '[data-component-id="paltana:back_to_top"]', context);
5      back_to_tops.forEach((back_to_top) => {
6        back_to_top.addEventListener('click', scrollToBottomChangeManager);
7      });
8
9      function scrollToBottomChangeManager(inputEvent) {
10        window.scrollBy(0, -window.innerHeight);
11      }
12
13      const bodys = once('scrollToBottomDetectbottom', 'body', context);
14      bodys.forEach((body) => {
15        window.addEventListener('scroll', scrollManager);
16      });
17
18      function scrollManager() {
19        if (window.pageYOffset > window.innerHeight) {
20          document.querySelector('[data-component-id="paltana:back_to_top"]').classList.remove('is-inactive');
21        }
22        else {
23          document.querySelector('[data-component-id="paltana:back_to_top"]').classList.add('is-inactive');
24        }
25      }
26    },
27  };
28})(Drupal);