This is what i tried to do, but I kept overthinking it and ended up with a much verbose and confusing code. Ill consider this approach in the future!

Observation: though the kata description don't ask for it, it's a good practice to copy the original array and work with it, since the sort method mutate the original array. I like to copy the original with slice method before applying any other method to the array.

I'm learning and I have a question, If 'str' is empty, it returns null and should return []. How does the test pass?
It's a great solution

Mindblowing

https://www.codewars.com/kata/reviews/559595019987562910000014/groups/55a86c703c84d58b2e0000fc is O(n)

Does anyone know the O(n) solution?

What is the O(n) solution?

good idea!!

...in spite of it being patched by the author.

This is amazing

this solution gonna return null if the str is empty, but the expected is[]

This is O(n logn) and it can be solved in O(n)

http://jsbench.github.io/#8deeaa709f814a7c78d502898c99a181

why this is best practice? its 10x slower than substring http://jsbench.github.io/#9cb819bf1ce429575f8535a211f72d5a