code: function addUnscrollClassName() {
        if (document.getElementById('unscroll-class-name')) {
          return;
        }
        var css = '.unscrollable { overflow-y: hidden !important; }',
          head = document.head || document.getElementsByTagName('head')[0],
          style = document.createElement('style');
        style.type = 'text/css';
        style.setAttribute('id', 'unscroll-class-name');
        style.appendChild(document.createTextNode(css));
        head.appendChild(style);
      }
docs: Add unscroll class to head