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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.
That's a problem with your code, not a kata issue, print the input to help you debug your code and read the docs (like MDN) about the methods you use.