Very nice, but use double quotes for string interpolation only!

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'