Is there any way to convert string as object property in angular? eg:

```
getErrorMessage(error_type) {
    return this.userForm.controls.{error_type}.hasError('required') ? 'You must enter a value' : '';
}

getErrorMesssage('email');

```

The function should work something like 

```
return this.userForm.controls.email.hasError('required') ? 'You must enter a value' : '';

```