How would one begin doing this without using recursion?

I have tested my code on jsfiddle against the three given tests as well as my own, and they all passed. However, when I test here, I get:
Test didn't pass: Unknown error

Any ideas what's going on?

Edit: for some reason, I had to add one of my own tests here on codewars, then it ran the others? I didn't know we were required to write any of our own tests?

Edit: ohh, run tests is only for personal tests, got it.