I was about to edit it for you; if you need a hand (even like rewriting it all from scratch and leaving you with the kata as a draft), just ask :)

Btw, be sure to put at least some Test.assertSimilar (mostly if you need to return arrays on JS) or Test.assertEquals (for anything else) checkers in both the sample test cases and the full course of tests.

They are quite useful as they give out informative error messages and you can simply set them up like Test.assertEquals(yourfunctionname(testparameters),expectedresult,optional extra error message).

Maybe I just told you trivial things you already know, but, if you think I can help in some way improving this kata (I would also have some financial background, in case it may help), really be my guest :)