Create a form group with a group-level validator
You include group-level validators as the second arg, or group-level async validators as the third arg. These come in handy when you want to perform validation that considers the value of more than one child control.
const form = new FormGroup({
password: new FormControl('', Validators.minLength(2)),
passwordConfirm: new FormControl('', Validators.minLength(2)),
}, passwordMatchValidator);
function passwordMatchValidator(g: FormGroup) {
return g.get('password').value === g.get('passwordConfirm').value
? null : {'mismatch': true};
}