https://www.usvotefoundation.org/vote/js/affix.js;jsessionid=DE453539C4167227822F0FAD3F6389B9

1(function ($) {
2  $(function () {
3    var toggleAffix = function (affixElement, scrollElement, wrapper) {
4
5      var height = affixElement.outerHeight(),
6        top = wrapper.offset().top;
7
8      if (scrollElement.scrollTop() > top) {
9        wrapper.height(height);
10        affixElement.addClass("affix");
11      }
12      else {
13        affixElement.removeClass("affix");
14        wrapper.height('auto');
15      }
16
17    };
18
19    $('[data-toggle="affix"]').each(function () {
20      var ele = $(this),
21        wrapper = $('<div></div>');
22
23      ele.before(wrapper);
24      $(window).on('scroll resize', function () {
25        toggleAffix(ele, $(this), wrapper);
26      });
27
28      // init
29      toggleAffix(ele, $(window), wrapper);
30    });
31  });
32})(jQuery);