// assume /foo.json is {"foo":"some value"}
declareUpdate();
var doc = cts.doc("/foo.json");
var docObj = doc.toObject();
docObj.foo = "this is a different value";
xdmp.nodeReplace(doc, docObj); 
// now /foo.json will look like: {"foo":"this is a different value"}

// create an XML document

declareUpdate();
xdmp.documentInsert("/example.xml", xdmp.unquote(
  '<a><b>bbb</b></a>').next().value);

******
// replace the b node with a c node

declareUpdate();
var n = new NodeBuilder();
// create a <c>ccc</c> node
node = n.addElement("c", "ccc").toNode();
xdmp.nodeReplace(cts.doc("/example.xml").xpath("/a/b"), node);

******
// look at the new document

cts.doc("/example.xml");
 =>
<?xml version="1.0" encoding="UTF-8"?>
<a><c>ccc</c></a>
  

// This example shows how to update the root
// node of a text format document.  Start by
//   creating a text document.     

declareUpdate();
var n = new NodeBuilder();
node = n.addText("This is a line of text.").toNode();
xdmp.documentInsert("/mydir/doc.txt", node);

******

//  Update the text node of the text document
//  by appending another line of text to the
//  text node.  Note that the text node is the
//  root node of a text document.     

declareUpdate();
var newText = fn.concat(cts.doc("/mydir/doc.txt"), "\n\
This is another line of text.");
var n = new NodeBuilder();
node = n.addText(newText).toNode();
xdmp.nodeReplace(cts.doc("/mydir/doc.txt").xpath("/text()"), node);

*****

// look at the updated document
cts.doc("/mydir/doc.txt")
=>
This is a line of text.
This is another line of text.

// create a document
declareUpdate();
xdmp.documentInsert("/foo.json", {"foo":"this is a value"});

******
// replace the value using xdmp.nodeReplace
declareUpdate();
var n = new NodeBuilder();
node = n.addText("this is a different value").toNode();
xdmp.nodeReplace(cts.doc("/foo.json").xpath("/foo"), node);

******
// show the new doc
cts.doc("/foo.json");
=>
{"foo":"this is a different value"}