Window.prototype.printNode= function (el) {
  return (new XMLSerializer()).serializeToString(el);
 };

Window.prototype.parseXML = function (s,doc) {
 if (doc==null) {
  doc=(new DOMParser()).parseFromString(s, "text/xml");
  return doc;
 } else {
  var doc2=(new DOMParser()).parseFromString(s, "text/xml");
  doc.importNode(doc2, true)
  return doc2;
 }
}