code: function(el, prefix) {
              prefix = prefix || 'yui-gen';
  
              var f = function(el) {
                  if (el && el.id) { // do not override existing ID
                      YAHOO.log('generateId returning existing id ' + el.id, 'info', 'Dom');
                      return el.id;
                  }
  
                  var id = prefix + YAHOO.env._id_counter++;
                  YAHOO.log('generateId generating ' + id, 'info', 'Dom');
  
                  if (el) {
                      if (el[OWNER_DOCUMENT] && el[OWNER_DOCUMENT].getElementById(id)) { // in case one already exists
                          // use failed id plus prefix to help ensure uniqueness
                          return Y.Dom.generateId(el, id + prefix);
                      }
                      el.id = id;
                  }
                  
                  return id;
              };
  
              // batch fails when no element, so just generate and return single ID
              return Y.Dom.batch(el, f, Y.Dom, true) || f.apply(Y.Dom, arguments);
          }
docs: Returns an ID and applies it to the element "el", if provided.
  @method generateId
  @param {String | HTMLElement | Array} el (optional) An optional element array of elements to add an ID to (no ID is added if one is already present).
  @param {String} prefix (optional) an optional prefix to use (defaults to "yui-gen").
  @return {String | Array} The generated ID, or array of generated IDs (or original ID if already present on an element)