getElementsByTagNameNS

getElementsByTagNameNS is a method of the Element interface in the Document Object Model (DOM) that returns a live NodeList of all descendant elements that have a specific tag name and namespace. It is used to select elements within an XML or HTML document based on both their tag name and the namespace they belong to. This is particularly useful when dealing with XML documents that use namespaces to organize elements.

The method takes two arguments: namespaceURI and localName. The namespaceURI is a string representing the namespace of the elements to be found, and localName is a string representing the tag name of the elements. If the namespaceURI is null, it will match elements that do not belong to any namespace. If localName is an asterisk (*), it will match all elements within the specified namespace regardless of their tag name.

The returned NodeList is live, meaning that if elements matching the criteria are added to or removed from the document, the NodeList will be updated automatically to reflect these changes. This can be efficient for dynamic content. However, it is important to be aware of this live nature when iterating over the NodeList, as modifications during iteration can lead to unexpected behavior. getElementsByTagNameNS is a powerful tool for precisely selecting elements in complex XML structures.