code: function (index) {
              var self = this;
              if (typeof index === 'number') {
                  if (index >= self.length) {
                      return null;
                  } else {
                      return new Node(self[index]);
                  }
              } else {
                  return new Node(index);
              }
          }
docs: Get one node at index
  @param {Number} index Index position.
  @return {KISSY.Node}