object-node(), array-node(),
text(), number-node(), boolean-node(),
null-node(), or document-node().
An object-node() atomizes as a json:object.
An array-node() atomizes as a json:array.
A null-node() atomizes as an empty sequence.
A boolean-node() atomizes as an xs:boolean.
A number-node() atomizes as an xs:integer,
xs:decimal, or xs:double value.
A text() node atomizes as an xs:untypedAtomic.
A document-node() atomizes the same as its root.
This function returns the same result as fn:data,
but it only works on JSON nodes.
To make a JSON node from a string, use xdmp:unquote
with the "format-json" option.
xdmp.fromJSON(xdmp.unquote('["a", null, false]',null,"format-json"));
=>
["a", null, false]
var str = '[{"some-key":45683}, "this is a string", 123]';
var node = xdmp.unquote(str,null,"format-json");
xdmp.fromJSON(node);
=>
[{"some-key":45683}, "this is a string", 123]