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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
I think this solution is difficult.Please, read about Big^O^notation
str.split(...)makes strings be corrupted (eg. emojis are splited into 2 codepoints).Better use
Array.from(str)to convert it to array safetyreturn "nothing" - is a kind of "dead code" so you will never reach that return statement