Angular is automatically adding 'ng-invalid' class on 'required' fields

Question

I am building an angular app for which I have some forms set up. I have some fields that are required to be filled before submission. Therefore I have added \'required\' on

Answer 1

the accepted answer is correct.. for mobile you can also use this (ng-touched rather ng-dirty)

input.ng-invalid.ng-touched{
  border-bottom: 1px solid #e74c3c !important; 
}