Open XML and using xslt with JavaScript

Question

Hello,
I want the user to be able to choose an XML-file. This XML-file should not be placed in InDesign, there is not even a document needed for my script. All I need is a variable, containing the file. However, the XML-file should be transformed with xslt into another XML-file. How do I do this?
This is how I open the first XML-file, the one that should be transformed:
   var xmlDoc = File.openDialog ("Choose XML");
   if (xmlDoc == null) {return;}
    xmlDoc.open("r");
    xmlDoc = xmlDoc.read();
    xmlDoc = new XML(xmlDoc);
I can adress different nodes and use xmlDoc as an XML-file, so that's fine, but how do I transform it?
I read the Scripting Guide and tried this:
    var myDocument = app.documents.add();
    var myXMLImportPreferences = app.xmlImportPreferences;
    myXMLImportPreferences.transformFilename = "c:\myTransform.xsl";
    var xx = myDocument.importXML(File.openDialog ("XML"));
However, it's not exactly what I want since I have to create a document and it's not working either, since xx stays undefined.
Thanks for your help.

Answer 1

You can't get exactly what you want.
Your first code example uses the InDesign JavaScript interpreter's XML support, called E4X. It has absolutely nothing to do with the InDesign document object model or InDesign's internal support for XML. It exists only within the JavaScript interpreter. It does not support XSLT transformations.
Your second example leverages InDesign's built-in XSLT support (I'm not too sure how this works...); but that is only useful when importing XML into
InDesign, which, as you have learned, requires a document.
In the first example, you could call out to an external invokation of xsltproc and read in the input. How to do that differs for Windows and Mac.
In the second example, you could export the XML from your Document back out to an XML file and read it back in with E4X.
None of this is very appealing. What do you really need to do?