code: function(node, className) {
          if (!Y.DOM.hasClass(node, className)) { // skip if already present 
              node.className = Y.Lang.trim([node.className, className].join(' '));
          }
      }
docs: Adds a class name to a given DOM element.
  @method addClass
  @for DOM
  @param {HTMLElement} element The DOM element.
  @param {String} className the class name to add to the class attribute