function.js

    // on hashchange
    window.addEventListener('hashchange', function (event) {
      // grab the hash
      var hash = location.hash.split('#')[1]
      // grab the links with selectable class
      var links = document.querySelectorAll('a.selectable')
      // loop through the links
      for (var i = 0; i < links.length; i++) {
        // if the hash matches the href of the link
        var href = links[i].href.split('#')[1]
        if (hash === href) {
          // change the style
          links[i].classList.add()
        } else {
          links[i].classList.remove()
        }
      }
    }, false)