xml for SCRIPT

I have an xml file that contains ~200 elements(each
containing 14-25 children).

Since I didn't see a way to open a file using xmljs, I
have my php output the file into a JS string called
"xml". I then follow the example and do:
var parser = new DOMImplementation();
var domDoc = parser.loadXML(xml);

It is at this point the my browser seemingly locks up.
I have to tell Firefox to "Continue" ~4 times before
the script finally gets past the loadXML line.

Is this normal? Is there a faster way to load up the
domDoc? Or perhaps a way to open a file directly(if
it's the string parsing that is causing the slowdown)?