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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.
In this case the regular expression will ignore the underscore in the return value, since it cannot be paired with another character.
But what if the length of the string is a even number?
Can someone please explain why adding || [] can solve the null.length error. what's the raason behind it. Thanks in advance!