A ng-model is a form input property to two-way bind in a form control model. We are declared n number of ng-models, This model requires a validation for directive and component side also. Most of the user experience is apply with in directive because of didn't ready to waste the time to submit a form and validate in server side. In line validation, the very important role is played in angular and bootstrap framework. This form validation is declared a mandatory property in mg-model means bootstrap is binding in a directive for a hash class in angular. Form Validation states: State Class if true Class if false The control has been visited. ng-touched ng-untouched The control's value has changed. ng-dirty ng-pristine The control's value is valid. ng-valid ng-invalid Example: < input type = "text" ...