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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.
This basically means "Give me an array of letters from sorted input array's first item" ;)
You need to wrap those values with brackets
[], because what you posted isn't an array. Using "3 dots" on a string returns an array of characters.See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax