(solved ) Why does it not work?

Question

When I try to use this calculator, I get the Nan (not a number) error.
Does anybody know why?
https://code.sololearn.com/W8Zb963TyE3N/?ref=app

Answer 1

I hope helpfulness

https://code.sololearn.com/WU881juu05Ri/?ref=app

Answer 2

Thanks!!!

Answer 3

In the "regnut" function, you got the numbers by .value, which is only working for inputs.
You should use .innerHTML