Deserializing and Serializing with XMLDocument | Parsing and XMLDocument from its string representation, cloning its inner element and appending to its parent ..

clone.and.append.element.into.XmlDocument.js

class XMLHelper {
	static isValid(xmlDocument) {
		return (xmlDocument && !xmlDocument.getElementsByTagName('parsererror').length);
	}
	static deserialize(xmlString) {
		return (new DOMParser()).parseFromString(xmlString, "application/xml");
	}
	
	static serialize(xmlDocument) {
		return (new XMLSerializer()).serializeToString(xmlDocument);
	}
}

var xmlString = `<?xml version="1.0" encoding="UTF-8"?>
<catalog>
    <cd>
        <title>empire burlesque</title>
        <artist>bob dylan</artist>
        <country>usa</country>
        <company>columbia</company>
        <price>10.90</price>
        <year>1985</year>
    </cd>
    <cd>
        <title>hide your heart</title>
        <artist>bonnie tyler</artist>
        <country>uk</country>
        <company>cbs records</company>
        <price>9.90</price>
        <year>1988</year>
    </cd>
</catalog>`;

function doTheThing(xmlString){
	var node = null, doc = XMLHelper.deserialize(xmlString);
	if(!XMLHelper.isValid(doc)) {
		return console.log((node = doc.querySelector('parsererror')) ? node.textContent : 'error while parsing xml');
	}
	(node = doc.querySelector('catalog cd')) && (node = node.parentNode.appendChild(node.cloneNode(true))) && (node.id = (new Date()).getTime());
	doc = XMLHelper.serialize(doc);
	console.log(doc);
}

doTheThing(); // error..
doTheThing(xmlString); // success...

live @ https://jsbin.com/seyamac/edit?js,console