I feel that although this is pretty clever, it's completely unreadable. I'm sure I could break it down and figure out where each part is coming from, but I feel that I shouldn't have to do this.

I imagine you completed it just seeing if you could do it this way, but in case others see this and say, "oh, that's a smart way of doing this. I think I'll do it," I wanted to make it clear this is very unreadable and not friendly to other developers.

I really like the const result = signature.slice(0, n); instead of adding slice on the result. I think it's cleaner from the start.