That's clever! I like this solution.

lol, that is actually the only unit test I used, and my answer is 2. I think both opinion makes sense.

This works depending on the parameters of the problem:
Should the following function return 1 or 2?

solution('bbb','bb')

It's performance varies with browser, FF 25 for instance is faster at regex on my laptop (split is 32% slower than regex), Chrome 30 is 64% slower for regex than join (and chrome regex performs over 200,000 ops less than FF in the test time)

The exception breaks the forEach when the item is found.