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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.
sure, ES6 changes everything!
"the author" doesn't remember this specific kata, but it's quite possible I didn't know how to do something :). Fairly new to ruby.
So I guess the reason the author extracted the indexes of the original array into the new array is because he didn't know to get the index of a specific element in the original array after he sorted the original array?