Element: localName property

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:svg="http://www.w3.org/2000/svg">
<head>
  <script><![CDATA[
function test() {
  const text = document.getElementById("text");
  const circle = document.getElementById("circle");

  text.value = `<svg:circle> has:
localName = "${circle.localName}"
namespaceURI = "${circle.namespaceURI}"`;
}
  ]]></script>
</head>
<body onload="test()">
  <svg:svg version="1.1"
    width="100px" height="100px"
    viewBox="0 0 100 100">
    <svg:circle cx="50" cy="50" r="30" fill="#aaaaaa" id="circle"/>
  </svg:svg>
  <textarea id="text" rows="4" cols="55"/>
</body>
</html>

<comm:business id="soda_shop" type="brick_n_mortar" xmlns:comm="http://example.com/comm">
  <comm:partners>
    <comm:partner id="1001">Tony's Syrup Warehouse
    </comm:partner>
  </comm:partner>
</comm:business>