AsyncValidatorFn - Angular

A function that receives a control and returns a Promise or observable that emits validation errors if present, otherwise null.

API

interface AsyncValidatorFn {
  (control: AbstractControl<any, any, any>): Promise<ValidationErrors | null> | Observable<ValidationErrors | null>;
}

Promise<ValidationErrors | null> | Observable<ValidationErrors | null>

@paramcontrolAbstractControl<any, any, any>

@returnsPromise<ValidationErrors | null> | Observable<ValidationErrors | null>