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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.
Is not a bad solution, but what he is doing with the for loop + if is the definition of Array.filter(), so this is unnecessarily large, you should always use .filter() in this situation.
What is the time complexity for this?
Agree. This should be the best practice. Easy to understand and light to perform.