code: function browserScrollbarWidth () {
          var testEl;
  
          if ( _scrollbarWidth === undefined ) {
  
              testEl = document.createElement( "div" );
              testEl.style.cssText = "width: 100px; height: 100px; overflow: scroll; position: absolute; top: -500px; left: -500px; margin: 0px; padding: 0px; border: none;";
  
              document.body.appendChild( testEl );
              _scrollbarWidth = testEl.offsetWidth - testEl.clientWidth;
              document.body.removeChild( testEl );
  
          }
  
          return _scrollbarWidth;
      }
docs: Does the actual work of $.scrollbarWidth. Protected from external modification. See $.scrollbarWidth for details.
  
  Adapted from Ben Alman's scrollbarWidth plugin. See
  - http://benalman.com/projects/jquery-misc-plugins/#scrollbarwidth
  - http://jsbin.com/zeliy/1
  
  @returns {number}