code: function _getElement(name, parentNode) {
      if (name === '') name = null;
      var _elem;
      var _isarr = false;
      if (typeof name === 'string') {
        if (name[0] == '<') {
          _elem = window.document.createElement('div');
          _elem.innerHTML = name;
          if (_elem.childNodes.length == 1) {
            _elem = _elem.childNodes[0];
            _isarr = false;
          }
          else {
            _elem = _elem.childNodes;
            _isarr = true;
          }
        }
        else {
          if (name.indexOf('<') > 0 || name.indexOf('>') > 0)
            throw new Error('Syntax error, unrecognized');
  
          var names = name.split(' ');
          var nodes = parentNode ? [parentNode] : null;
          for (var i = 0; i < names.length; i++) {
            if (names[i] != '')
              nodes = _matchElement(nodes, names[i], !!parentNode);
          }
          if (nodes.length <= 1) {
            _elem = nodes[0];
            _isarr = false;
          } else {
            _elem = nodes;
            _isarr = true;
          }
        }
      } else {
        _elem = name;
      }
      return {_elem, _isarr};
    }
docs: - parentNode 仅筛选此节点下的节点.