Field State (touched, dirty, pristine, valid)

Angular tracks the state of form fields.

Common field states:

• touched – field has been visited
• dirty – value has changed
• pristine – value has not changed
• valid – field passes validation
• invalid – field fails validation

<input name="username" ngModel #username="ngModel">

<div *ngIf="username.touched && username.invalid">
  Invalid username
</div>