How to parse HTML from JavaScript in Firefox?

Question

What is the best way to parse (get a DOM tree of) a HTML result of XmlHttpRequest in Firefox?

EDIT:

I do not have the DOM tree, I want to acquire i

Answer 1

At least for newer Firefox versions, an easier way is or will soon be available.

https://developer.mozilla.org/en/HTML_in_XMLHttpRequest indicates that starting from FF11 it will be possible to ask for a DOM directly from the XHR by setting the responseType attribute to "document". At that point, the HTML will be parsed and the DOM stuck into responseXML as for an XML document.