function isIPv4Address(inputString: string): boolean {
  const parts = inputString.split(".");

  for (const v of parts) {
    const n = Number(v);
    if (v === "" || Number.isNaN(n) || n > 255 || v !== String(Math.trunc(n))) {
      return false;
    }
  }

  return parts.length === 4;
}