Nice functional style. I like it. It is very easy to see what is going on.

Thank you :) I wasn't aware of this javascript quirk. What I don't understand now is why cheating solutions gets upvotes or why people even submit them. Sure, it is interesting hack and I learned something new, but isn't the idea of this exercises to see how some problems can be approached differently (and sometimes presumably better) than you.

Can someone please explain this solution to me? I will be very grateful.

I ran into the exact same issue but I managed to solve it. It was related to incorectly entering the [] loop.