n null;
              }
              
              if (document.documentElement.scrollTop >= elem.offsetTop) {
                if (tableOfContentsElem) {
                  var id = elem.getAttribute('id');
                  tocElem.querySelectorAll('a').forEach(function (elem) {
                    elem.classList.remove('active');
                  });
                  tocElem.querySelector('a[href="#' + id + '"]') ?
                    tocElem.querySelector('a[href="#' + id + '"]').classList.add('active