JSFiddle - React, Tailwind, and code Playground

JavaScript

var parseXml;

if (typeof window.DOMParser != "undefined") {
    parseXml = function(xmlStr) {
        return ( new window.DOMParser() ).parseFromString(xmlStr, "text/xml");
    };
} else if (typeof window.ActiveXObject != "undefined" &&
       new window.ActiveXObject("Microsoft.XMLDOM")) {
    parseXml = function(xmlStr) {
        var xmlDoc = new window.ActiveXObject("Microsoft.XMLDOM");
        xmlDoc.async = "false";
        xmlDoc.loadXML(xmlStr);
        return xmlDoc;
    };
} else {
    throw new Error("No XML parser found");
}

var xml = parseXml("<Response attr1='hello' bar='{ \"int\": 50, \"bool\": false, \"message\":\"&lt; message &gt; Test Message &lt;a href=\"http://www.blah.com\"&gt;here&lt;/a&gt;  &lt; /message &gt;\" }'/>");

var realityCheckNode = xml.getElementsByTagName("Response")[0];
document.body.innerHTML = realityCheckNode.getAttribute("bar");