If your input was say '123', both would return the same result, i.e., 123. But if your input included other characters, e.g. '123a', this solution would return NaN and the other one 123

wow this is pretty easy

I committed an equally wrong solution just to see whether it works. I assume/hope some of these warriors were just trying the same thing.

There should be a way to down vote this one.

Fail if index == items.length

Amazing, this is wrong and gets three upvotes for best practices??? Can we downvote solutions?

Yes, you're right, it's a classic off-by-one error.

The testcases are not picking it up, though.

I believe this solution returns the wrong result:

items = ['a','b','c']
solution(items,3,'d')
=> nil

but should be 'd'