I struggle with Arithmetic Formatter

Hi! I’m struggling with this challenge for a long time. I watched tutorials, forum posts, etc, etc for guiding me but even with all of that I can’t figure out what is the problem with my code. On top of that, I can’t read correctly the console for see what are the errors those are throwing at me.

I will be so glad if you can help me because i am stuck and i need my certification : c

Thank you!
Link my project: boilerplate-arithmetic-formatter - Replit

OH Thanks . I even dont realize that