Well holy crap. In all my years of screwing up javascript, that's the first time I've heard of sort() being so unstable. Sure enough, it was an easy fix. Thanks a bunch!

If you run the code that I've provided, you'll see that Kata is incorrectly showing something didn't pass, when it in fact DID pass. That's what I'm getting at there. Try my code in your browser console and it will pass 100% of the time. Try the exact same code in Kata, and it fails. This one isn't resolved.

Try:
isIsoGram("bncwxyfvesoriXljhmzputkgdaq");

Codewars returns: Expected: false, instead got: true
Console Returns : false