https://www.ristorantedoncarlos.it/sites/doncarlos.gisnet.it/themes/bootstrap_barrio/js/affix.js?v=8.9.7

1/**
2 * @file
3 * Affix for Bootstrap 4.
4 * https://www.codeply.com/users/skelly
5 *
6 */
7(function ($, Drupal) {
8
9  'use strict';
10
11  Drupal.behaviors.bootstrap_barrio_affix = {
12    attach: function (context, settings) {
13      var toggleAffix = function (affixElement, scrollElement, wrapper) {
14
15        var height = affixElement.outerHeight(),
16            top = wrapper.offset().top;
17
18        if (scrollElement.scrollTop() >= top){
19            wrapper.height(height);
20            affixElement.addClass("affix");
21        }
22        else {
23            affixElement.removeClass("affix");
24            wrapper.height('auto');
25        }
26
27      };
28
29      $('[data-toggle="affix"]').once().each(function () {
30        var ele = $(this),
31            wrapper = $('<div></div>');
32
33        ele.before(wrapper);
34        $(window).on('scroll resize', function () {
35            toggleAffix(ele, $(this), wrapper);
36        });
37
38        // init
39        toggleAffix(ele, $(window), wrapper);
40      });
41    }
42  }
43})(jQuery, Drupal);