// Adds up the values listed in a sample XML document and adds a new element with the total.
var xml = '<things>'
+ '<plates>12</plates>'
+ '<bowls>18</bowls>'
+ '<cups>25</cups>'
+ '</things>';
var document = XmlService.parse(xml);
var root = document.getRootElement();
var items = root.getChildren();
var total = 0;
for (var i = 0; i < items.length; i++) {
total += Number(items[i].getText());
}
var totalElement = XmlService.createElement('total').setText(total);
root.addContent(totalElement);
xml = XmlService.getPrettyFormat().format(document);
Logger.log(xml);
A representation of an XML Element node.