<!DOCTYPE html>
<html lang="en-US">
<body>
<p>Click the button to find out if the specified namespace is default.</p>
<button onclick="myFunction()">Click Me</button>
<script>
function myFunction() {
var doc = document.documentElement;
var result = doc.isDefaultNamespace("http://www.w3.org/1999/xhtml");
alert(result);
}
</script> </body>
</html>