https://www.lannoopublishers.com/sites/all/modules/custom/lea_contact/js/lea_contact.js?tm4xxp

1(function ($) {
2  Drupal.behaviors.lea_contact = {
3    attach: function (context, settings) {
4      $('#wrapper-middle').append('<div class="scroll-top-wrapper"><a id="scroll-top">Top</a></div>');
5      $('#scroll-top').hide();
6
7      if ($(window).width() <= '480') {
8        $(window).on('scroll', function () {
9          var scrollTrigger = 100; // px
10          var scrollTop = $(window).scrollTop();
11          if (scrollTop > scrollTrigger) {
12            $('#scroll-top').show();
13          } else {
14            $('#scroll-top').hide();
15          }
16        });
17      }
18      $('#wrapper-middle #scroll-top').on('click', function (e) {
19        e.preventDefault();
20        $('body').animate({scrollTop: 0}, '0.2');
21      });
22    }
23  }
24})(jQuery);