<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<body>
<p id="demo">Click the button get the URI of the document's namespace</p>
<button onclick="myFunction()">Try it</button>
<script>
function myFunction()
{
var x=document.getElementById("demo");
x.innerHTML=document.documentElement.namespaceURI;
}
</script>
<p><strong>Note:</strong> Internet Explorer 8 and earlier does not support the namespaceURI property.</p>
</body>
</html>