Understanding the Angular ngModel and Form Control States

The form control class .ng-dirty is the correct Angular class that's assigned to an input field when its value is modified. This class is generally used in conjunction with Angular's two-way data binding feature encapsulated by [(ngModel)].

Angular provides a powerful template-driven form module that allows us to easily track and validate user inputs, and the .ng-dirty class is a part of this system. This class is automatically added by Angular to input elements whenever the user modifies the initial content.

This allows you to add visual cues to your forms to indicate which fields have been modified. For instance, you can use CSS to change the styling of .ng-dirty inputs to alert users that they have unsaved changes:

input.ng-dirty {
  background-color: #fcf8e3;
}

In this example, any input that has been modified would have a light yellow background.

Now, you might be wondering about the other classes. They also represent different states of form controls:

• .ng-invalid: This class applies when the form control doesn't meet the validation conditions.
• .ng-pending: This class applies when asynchronous validation is in progress.It disappears once the validation is complete.
• .ng-pristine: Angular sets this class if a user has not yet modified an input field in the form.

Following best practices regarding form design will provide better user experience and data integrity. Always ensure you use form validation. Combining tools like .ng-dirty and .ng-invalid, you can tailor your form's user interface to guide users into providing correct information and alert them to errors before they submit.

Armed with this knowledge, you're ready to create more responsive, user-friendly forms using Angular's [(ngModel)] and form control classes.