code: function setClasses( classes ) {
      var className = docElement.className;
      var classPrefix = Modernizr._config.classPrefix || '';
  
      // Change `no-js` to `js` (we do this independently of the `enableClasses`
      // option)
      // Handle classPrefix on this too
      if(Modernizr._config.enableJSClass) {
        var reJS = new RegExp('(^|\\s)'+classPrefix+'no-js(\\s|$)');
        className = className.replace(reJS, '$1'+classPrefix+'js$2');
      }
  
      if(Modernizr._config.enableClasses) {
        // Add the new classes
        className += ' ' + classPrefix + classes.join(' ' + classPrefix);
        docElement.className = className;
      }
  
    }
docs: Pass in an and array of class names, e.g.: ['no-webp', 'borderradius', ...]