DOMParser

const parser = new DOMParser();
const doc = parser.parseFromString(stringContainingXMLSource, "application/xml");

<parsererror xmlns="http://www.mozilla.org/newlayout/xml/parsererror.xml">
(error description)
<sourcetext>(a snippet of the source XML)</sourcetext>
</parsererror>

const xmlDoc = new DOMParser().parseFromString(stringContainingXMLSource, "application/xml");
// returns a Document, but not a SVGDocument nor a HTMLDocument

const svgDoc = new DOMParser().parseFromString(stringContainingXMLSource, "image/svg+xml");
// returns a SVGDocument, which also is a Document.

const htmlDoc = new DOMParser().parseFromString(stringContainingHTMLSource, "text/html");
// returns a HTMLDocument, which also is a Document.

/* inspiriert von https://gist.github.com/1129031 */
/*global document, DOMParser*/

(function(DOMParser) {
    "use strict";

    const proto = DOMParser.prototype;
    const nativeParse = proto.parseFromString;

    // Firefox/Opera/IE werfen bei unbekannten Typen Fehler
    try {
        // WebKit gibt bei bei unbekannten Typen `null` zurück
        if (new DOMParser().parseFromString("", "text/html")) {
            // text/html wird unterstützt
            return;
        }
    } catch (ex) {}

    proto.parseFromString = function(markup, type) {
        if (/^\s*text\/html\s*(?:;|$)/i.test(type)) {
            const doc = document.implementation.createHTMLDocument("");
            if (markup.toLowerCase().includes('<!doctype')) {
                doc.documentElement.innerHTML = markup;
            } else {
                doc.body.innerHTML = markup;
            }
            return doc;
        } else {
            return nativeParse.apply(this, arguments);
        }
    };
}(DOMParser));