function getChildren( elem ){
   var child = elem.firstChild, res = [];
   while ( child ) {
      if ( child.nodeType == 1 ) {
          res [ res.length ] = child;
      }
      child = child.nextSibling;
   }
   return res;
}
var childrenNode = getChildren( node );
var firstChild = childrenNode.length ? childrenNode[0] : null;
var lastChild = childrenNode.length ? childrenNode[res.length - 1] : null;