fn:root

fn:root(
   [$arg as node()?]
) as node()?

Summary

Returns the root of the tree to which $arg belongs. This will usually, but not necessarily, be a document node.

If $arg is the empty sequence, the empty sequence is returned.

If $arg is a document node, $arg is returned.

If the function is called without an argument, the context item is used as the default argument. If the context item is undefined an error is raised: [err:XPDY0002]. If the context item is not a node an error is raised: [err:XPTY0004].

Example

Assume the following variable definitions:
let $i := <tool>wrench</tool>
let $o := <order> {$i} <quantity>5</quantity> </order>
let $odoc := document {$o}
let $newi := $o/tool

fn:root($i) returns $i
fn:root($o/quantity) returns $o
fn:root($odoc//quantity) returns $odoc
fn:root($newi) returns $o

Example

var doc = fn.head(xdmp.unquote('<a><quantity>5.0</quantity></a>')
    );
var elem = doc.root;
fn.root(elem).xpath("/a/quantity");
=> <quantity>5.0</quantity>