Calling makeSum twice per iteration is now a Best Practice ?!?

I had to update my solution and only now actually read the test cases. Great! :]

Also, changed vote and approved. Make more!

Thank-you for taking the time to explain this. I've updated the kata according to your suggestion.

Returning inconsistent datatypes is ++Ungood™ and should be avoided.

You could just as easily have the function return [ true, "original string" ], [ true, "" ] or even just [ true ] instead of true. That would enable you to always process the Boolean return value as answer[0]. As it is, the function always returns a truthy value and you need to Array.isArray() (or equivalent) the return value to find out whether or not to further process it. Which is senseless.

Edited! Thanks for the advice.

Instead of Answer is OK or Answer is not OK, the return value could be a boolean, so spelling would not matter. Otherwise it was a good excercise