1. DomName('Document.createElementNS')
  2. DocsEditable()
Element createElementNS(String namespaceURI, String qualifiedName, [String typeExtension])

Source 

@DomName('Document.createElementNS')
@DocsEditable()
Element createElementNS(String namespaceURI, String qualifiedName, [String typeExtension]) {
  var newElement = (typeExtension == null) ?
    _blink.BlinkDocument.instance.createElementNS_Callback_2_(unwrap_jso(this), namespaceURI, qualifiedName) :
    _blink.BlinkDocument.instance.createElementNS_Callback_3_(unwrap_jso(this), namespaceURI, qualifiedName, typeExtension);

  var wrapped;

  wrapped = js.getDartHtmlWrapperFor(newElement);  // Here's our Dart class.
  if (wrapped != null) {
    wrapped.blink_jsObject = newElement;
  } else {
    wrapped = wrap_jso(newElement);
    if (wrapped == null) {
      wrapped = wrap_jso_custom_element(newElement);
    } else {
      js.setDartHtmlWrapperFor(wrapped.blink_jsObject, wrapped);  // Here's our Dart class.
    }
  }

  return wrapped;
}