| <script> |
| |
| headings = []; |
| |
| onload = function(){ |
| headings = document.querySelectorAll('h2'); |
| }; |
| |
| onscroll = function(e){ |
| var heading = find(window.scrollY); |
| if (!heading) return; |
| var links = document.querySelectorAll('#menu a') |
| , link; |
| |
| for (var i = 0, len = links.length; i < len; ++i) { |
| link = links[i]; |
| link.className = link.getAttribute('href') == '#' + heading.id |
| ? 'active' |
| : ''; |
| } |
| }; |
| |
| function find(y) { |
| var i = headings.length |
| , heading; |
| |
| while (i--) { |
| heading = headings[i]; |
| if (y >= heading.offsetTop) { |
| return heading; |
| } |
| } |
| } |
| </script> |