JSFiddle - React, Tailwind, and code Playground

JavaScript

var xmlStr = "<doc><entry><child1> <child2> <child3 n='a'> </child3> </child2> </child1> </entry>";
xmlStr += "<entry> <child1> <child2> <child3 n='b'> </child3> </child2> </child1> </entry>";
xmlStr += "<entry> <child1> <child2> <child3 n='c'> </child3> </child2> </child1> </entry>";
xmlStr += "</doc>";

var xmlToString = function(oXML) {
  if (window.ActiveXObject) {
    return oXML.xml;
  } else {
    return (new XMLSerializer()).serializeToString(oXML);
  }
}

//From: http://stackoverflow.com/a/8412989/83418
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 xpath = "//entry[*/*/*[@n='c']]";
var xml = parseXml(xmlStr);
var element = xml.evaluate(xpath ,xml, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null);
var node = element.singleNodeValue;
node.parentNode.removeChild(node);

var updatedXml = xmlToString(xml);

alert(updatedXml);