With jquery, you can use $.parseXML(str), https://api.jquery.com/jQuery.parseXML/

https://github.com/abdmob/x2js - my own library (updated URL from http://code.google.com/p/x2js/):

This library provides XML to JSON (JavaScript Objects) and vice versa javascript conversion functions. The library is very small and doesn't require any other additional libraries.

API functions

• new X2JS() - to create your instance to access all library functionality. Also you could specify optional configuration options here
• X2JS.xml2json - Convert XML specified as DOM Object to JSON
• X2JS.json2xml - Convert JSON to XML DOM Object
• X2JS.xml_str2json - Convert XML specified as string to JSON
• X2JS.json2xml_str - Convert JSON to XML string

Online Demo on http://jsfiddle.net/abdmob/gkxucxrj/1/

var x2js = new X2JS();
function convertXml2JSon() {
    $("#jsonArea").val(JSON.stringify(x2js.xml_str2json($("#xmlArea").val())));
}

function convertJSon2XML() {
    $("#xmlArea").val(x2js.json2xml_str($.parseJSON($("#jsonArea").val())));
}

convertXml2JSon();
convertJSon2XML();
$("#convertToJsonBtn").click(convertXml2JSon);
$("#convertToXmlBtn").click(convertJSon2XML);

Using xml-js lib

import { json2xml } from "xml-js";

const input = {
  contact: {
    name: `John & cia "example"`
  }
};
const xml = json2xml(input, {
  compact: true
});

// <contact><name>John &amp; cia \"example\"</name></contact>

https://codesandbox.io/s/xml-json-forked-zgit4?file=/src/index.js:97-103

:)

I will have to look into XMLSerializer tomorrow. Here is the code I ended up writing instead, in case anyone is interested (requires prototype and FireBug for unknown nodes):

function extractXML(node) {
    switch (node.nodeType) {
        case 1: return extractNodeXML(node);
        case 2: return extractAttributeXML(node);
        // 3 = Text node
        case 3: return node.nodeValue;
        // 8 = Comment node - ignore
        case 8: return "";
        case 9: return extractDocumentNodeXML(node);
        case 10: return extractDocumentTypeXML(node);
        default: console.log(node); return "Unkwon type: "+node.nodeType;
    }
}
function extractNodeXML(node) {
    var xml = "<"+node.nodeName;
    $A(node.attributes).each(function (node) {xml += " "+extractXML(node)});
    xml +=">"
    $A(node.childNodes).each(function (node) {xml += extractXML(node)});
    xml += "</"+node.nodeName+">"
    return xml;
}
function extractAttributeXML(node) {
    return node.nodeName+"=\""+node.nodeValue+"\""
}
function extractDocumentNodeXML(node) {
    var xml = "<?xml version=\""+node.xmlVersion+"\" encoding=\""+node.xmlEncoding+"\"?>"
    $A(node.childNodes).each(function (node) {xml += extractXML(node)});
    return xml;
}
function extractDocumentTypeXML(node) {
    return "<!DOCTYPE "+node.name+" PUBLIC \""+node.publicId+"\" \""+node.systemId+"\">"
}

I haven't used this myself, but it seems like a good solution for anyone doing for a front-/back-end agnostic approach.

https://github.com/michaelkourlas/node-js2xmlparser