NG_VALIDATORS const    npm Package @angular/forms   Module import { NG_VALIDATORS } from '@angular/forms';   Source forms/src/validators.ts    const NG_VALIDATORS: any; Description Providers for validators to be used for FormControls in a form. Provide this using multi: true to add validators. Example @Directive({
  selector: '[custom-validator]',
  providers: [{provide: NG_VALIDATORS, useExisting: CustomValidatorDirective, multi: true}]
})
class CustomValidatorDirective implements Validator {
  validate(control: AbstractControl): ValidationErrors | null {
    return {"custom": true};
  }
}

    
{'path': 'public/docs/angular~5/api/forms/ng_validators.html', 'source': 'DevDocs.IO'}