How can I validate a phone number when prefix is selected but number not, but the field is not required?

[GabrielaCloudNine]

Now we apply the following check to omit the prefix, but is there a smarter way to valid it?

if (val?.length >= 5) {
      return matchIsValidTel(val);
}

[viclafouch]

Hello !

Not sure what you mean.. Please provide a codesandbox