code: function scrollbarWidth() {
      var d = document.createElement("scrolltester");
      d.style.cssText = 'width:100px;height:100px;overflow:scroll!important;position:absolute;top:-9999px;display:block';
      document.body.appendChild(d);
      var result = d.offsetWidth - d.clientWidth;
      document.body.removeChild(d);
      return result;
    }
docs: try to calculate the scrollbar width for your browser/os
  @return {Number}