are you referring to the index starting at 0

I was conflicted about that with confusing programmers. I figured there is enough context to understand that the index count started at 0.

If you can find my documentation that advises to not do that I can update it.

As for the check digit X I avoided it in the random tests for rust be could be an extra worth while challenge.

will add random tests for js

I think if ISBN-13 is novel enough for its own specification it is unique enough to combine it with a narrative and a more complex problem.

Yes as a 2nd Dan with 133k honor I understand how this isnt unique enough to you. But if we judge this based solely on how novel it is to a power user we should just delete most of 6kyu and below because they are all boiled down to an iterator with some maths.

Added an actual Javascript version with tests

Ah thank you sorry about that, new to submitting challenges. Thanks for catching that

Are you referencing ISBN-10 Validation?

I view this as a different problem given the addition of ISBN-13 and fuzzy string manipulation.

Oh lovely, I didn't know you could do that with =n to make it inclusive.