maybe this will help: JavaScript Style Guide

(re: Johan) Agreed, if you choose to author a kata, you should take responsibility for its entirety in its initial language.

Is this how I should do it?

Thanks to #Aza_rt random tests will be there soon.

Changed to closeTo()

fixed them

Done. Now it's 4 groups: 1-10, 11-20, 21-30, 31-40

Changed to pure set comparisons

I think a set would be appropriate.

Maybe put {2, 3, 10, 30} as a sample test?

You can't (neither can I). Let it be.

How can i delete this kata. Because it keep says "User does not have permission to perform this action" when i try to delete it.

The weird input and single character input mark the difference, so it's not a duplicate. So I think it's fine.