i mean yea, how i didn't think about it. Any books recomendation for algorithms?

Can you explain it somehow?

right now everything works but i keep getting this error

expected:<...wrtng s mng th wrst []'v vr rd> but was:<...wrtng s mng th wrst [I]'v vr rd>

does it have something so do with the fact i used a array?

any help is much appreciated

I've tried your code in repl.it and it works the same as here, you're only replacing one occurrence of each vowel.

My solution in other environments work well, but here say is not equal, and making a console.log i see it's equal

Please read this: https://docs.codewars.com/training/troubleshooting/#post-discourse

have you figure it out? It was quite challenging and satisfying to complete this task.