I have been using a DOMParser object to parse a text string to an XML tree. However it is not available in the context of a Web Worker (and neither is, of course, document.E
At this point I like to share my parser: https://github.com/tobiasnickel/tXml
with its tXml() method you can parse a string into an object and it takes only 0.5kb minified + gzipped