See https://wiki.whatwg.org/wiki/DOM_XSLTProcessor. Per https://github.com/whatwg/html/pull/738 this is implemented in all browsers now.
See https://wiki.whatwg.org/wiki/DOM_XSLTProcessor. Per whatwg/html#738 this is implemented in all browsers now.