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This is the archived documentation for Angular v17. Please visit angular.dev to see this page for the current version of Angular.

NG_VALIDATORS

An InjectionToken for registering additional synchronous validators used with AbstractControls.

      
      const NG_VALIDATORS: InjectionToken<readonly (Function | Validator)[]>;
    

See also

Usage notes

Providing a custom validator

The following example registers a custom validator directive. Adding the validator to the existing collection of validators requires the multi: true option.

      
      @Directive({
  selector: '[customValidator]',
  providers: [{provide: NG_VALIDATORS, useExisting: CustomValidatorDirective, multi: true}]
})
class CustomValidatorDirective implements Validator {
  validate(control: AbstractControl): ValidationErrors | null {
    return { 'custom': true };
  }
}