This is Fabian, I've been assigned to support your case.
I appreciate your interest in our products.
Could you please clarify if you have an NDA and, access to the MIFARE DESFire EV3 secure files?
Unfortunately, I'm not able to provide full support for a javascript-based application, but the issue you are having may be related to the endianness of the frames.
Best Regards,
Fabian