typia/src/internal/_isFormatHostname.ts

Superfast runtime validators with only one line

export const _isFormatHostname = (str: string): boolean => PATTERN.test(str);

const PATTERN =
  /^(?=.{1,253}\.?$)[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?(?:\.[a-z0-9](?:[-0-9a-z]{0,61}[0-9a-z])?)*\.?$/i;