Hey Hakan,
I played around bit with the auto-translation, and I confirm it doesn’t convert well for sum, append, and format. I’m not sure what the issue is with an empty list; that one seems to convert as I’d expect.
The annoying thing is that many of these functions are named differently in JS, and while we’re trying to cover such cases, it’s quite a project :). Let me tag @sotiri; he might find the cases you found interesting.
Good luck the course and sorry for the inconvenience!
Best, Thomas