Returns the namespace URI of one of the in-scope namespaces for $element,
identified by its namespace prefix.
fn:namespace-uri-for-prefix( $prefix as xs:string?,$element as element()xs:anyURI?If $element has an in-scope namespace whose namespace prefix is equal to
$prefix, the function returns the namespace URI of that namespace.
If $element has no in-scope namespace whose namespace prefix is equal to
$prefix, the function returns the empty sequence.
If $prefix is the zero-length string or the empty sequence, then if
$element has a default namespace (that is, a namespace node with no
name), the function returns the namespace URI of the default namespace. If
$element has no default namespace, the function returns the empty
sequence.
Prefixes are equal only if their Unicode codepoints match exactly.
let $e :=
The expression fn:namespace-uri-for-prefix("z", $e) returns "http://example.org/two".
The expression fn:namespace-uri-for-prefix("", $e) returns "http://example.org/one".
The expression fn:namespace-uri-for-prefix((), $e) returns "http://example.org/one".
The expression fn:namespace-uri-for-prefix("xml", $e) returns "http://www.w3.org/XML/1998/namespace".
The expression fn:namespace-uri-for-prefix("xml", $e) returns "http://www.w3.org/XML/1998/namespace".