nice

I'd say the main problem of your solution is that you are mutating the array and removing elements within your map function. The map function should only be used to map the elements to a different value, not to change the array itself. A function like reduce makes it more apparent that elements are being omitted.

You say that you didn't check the first letter, but that's actually correct as per description.

Somebody please review my solution, I guess it bad, because I didn't check register of first letter.

but looks good), i'm just a newby, and stil not pay attention for perfomance. Thanx for explanation!

its a bad solution. it uses sorting and has suboptimal performance.

I think it's awesome solution. I would like to solve in this way

great, thats what i can solve.

The original language is Ruby, which contains built-in methods to solve these katas. It may be not as simple in JS, but even then it would be a 7kyu, never 1.

but this is not looks like 8kuy.

Yes, hello. 8kyu are the easiest katas.

what? its 8kuy? its a joke, its 1. And I'm very stupid. I dont know how to solve and what to google

I spent 1 hour to solve it. I know its easy kata, very very easy, but 1 hour of solving, i'm very sad. I just googling methods, reading about them, and try to compile them rogether. But at the end I feel satisfaction. Thanx.

Practice makes perfect.