You are most welcome, glad to hear this helps! Give me a shout anytime if any of the code used above is unclear.
My go-to book for data transformations is the “JavaScript Pocket Reference” from David Flanagan btw (well, the German translation “JavaScript – kurz & gut” of it to be very precise). I can highly recommend it in case you’re still looking for a book to get. It’s not a complete guide on learning JavaScript but it has not let me down so far when I needed to transform data and didn’t know how.
What’s also worth keeping in mind when working with the Function node is the n8n data structure.