The getElementsByTagNameNS of Document for JS returns a HTMLCollection of all descendant elements if namespace and localName are "*".
If only namespace is "*", returns a HTMLCollection of all descendant elements whose local name is localName.
If only localName is "*", returns a HTMLCollection of all descendant elements whose namespace is namespace.
Otherwise, returns a HTMLCollection of all descendant elements whose namespace is namespace and local name is localName.
collection = document.getElementsByTagNameNS(namespace, localName)
A null or a non-empty string.