code: function(element, value) {
      var c, cl, className, classNames = [];
      if (typeof value === "string" && value) {
        classNames = value.split(/\s+/);
      }
      if (element && element.nodeType === 1 && classNames.length > 0) {
        className = (" " + (element.className || "") + " ").replace(/[\t\r\n\f]/g, " ");
        for (c = 0, cl = classNames.length; c < cl; c++) {
          if (className.indexOf(" " + classNames[c] + " ") === -1) {
            className += classNames[c] + " ";
          }
        }
        className = className.replace(/^\s+|\s+$/g, "");
        if (className !== element.className) {
          element.className = className;
        }
      }
      return element;
    }
docs: Add a class to an element, if it doesn't already have it.
  
  @returns The element, with its new class added.
  @private