From http://www.w3schools.com (Copyright Refsnes Data)

XML DOM getElementsByTagNameNS() Method

Definition and Usage

The getElementsByTagNameNS() method returns a NodeList of all elements with a specified name and namespace.

elementNode.getElementsByTagNameNS(ns,name)

Parameter	Description
ns	A string that specifies the namespace to search for. The value "*" matches all tags
name	A string that specifies the tagname to search for. The value "*" matches all tags

In all examples, we will use the XML file books_ns.xml, and the JavaScript function loadXMLDoc().

The following code fragment gets an element by tag name and namespace:

xmlDoc=loadXMLDoc("books_ns.xml");

x=xmlDoc.getElementsByTagNameNS("http://www.w3schools.com/children/","title");
document.write(x[0].nodeName);

Output:

c:title