Looks nice and clean, BUT it would fail with a subsequence of upper case letters (like "getURL")

split() probably just gets slices from the original string and doesn't actually "split" the string. I think that's why we can't then collect it to Vec<String> in hor_mirror() function, it collects only to vec of those slices.

You're so right bro!

JS being unable to implicitly compare BigInts with numbers 💀

These iterators are something from another world, but I'm gradually getting used to them.

The moment when I really appreciate arrow function's syntax

Because it's the initial value of the "sum" variable

You have to start working with optimizations at some point, and as hobovsky said, it's a very trivial one, in fact, if you read that part of the description again, you'll see this:

Looping all the way up to n, or n/2, will be too slow.

Pointing out where you should focus to make your code faster.

6 kyu is considered OK for challenges with trivial optimisations. Yellow kata are not beginner level anymore.

The rank is the only thing I'm mad about. I mean, 6 kyu is right next after "fundamentals" (which is 7-8), it's not fair to demand optimizations on this level.

But it doesn't, does it? Because it's too slow. There is a performance requirement, if your code isn't fast enough, it'll only work for a certain range. It's written in the kata's description. You can complain about the rank, that's fine, but you can't say that your code works when it doesn't.

This "too slow" condition is stupid as hell for 6 kyu. If the code works, it should be accepted.

DAMN

wait what D: