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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.
My suggestion was
[ this.slice() ]. It was about returning a consistently typed value.So return this.slice()
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True! Somehow an undefined turned into a null. :)
One of the test cases is broken:
Receiving: [ null, <1 empty item>, undefined, null, 0, '', <1 empty item>, [ <3 empty items> ], [] ]
Expected: [[null],[null,null,0,""],[ [null,null,null],[] ]]