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]) {
  return (typeExtension == null)
      ? _blink.BlinkDocument.instance
          .createElementNS_Callback_2_(this, namespaceURI, qualifiedName)
      : _blink.BlinkDocument.instance.createElementNS_Callback_3_(
          this, namespaceURI, qualifiedName, typeExtension);
}