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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.
Oh, thank you. Now it makes sence for me
what if first and last elements of iterable will be the same?
I mean if we pass '323' in the first iteration, i === 0 so [i-1] will compare first (0) and last (-1) elements and filter will return ['2', '3'].
Correct me if I mistaken but I'll rather use [i+1] for compare