isValidZipCode

1/**
2 * Validates if a string is a valid ZIP/postal code.
3 * Supports basic validation for US ZIP codes (5-digit or ZIP+4).
4 *
5 * @param zip - The ZIP code string to validate.
6 * @returns True if the string is a valid ZIP code.
7 */
8export function isValidZipCode(zip: string): boolean {
9  return /^\d{5}(-\d{4})?$/.test(zip);
10}

1test('validates 5-digit ZIP code', () => {
2  expect(isValidZipCode('12345')).toBe(true);
3});
4
5test('validates ZIP+4 format', () => {
6  expect(isValidZipCode('12345-6789')).toBe(true);
7});
8
9test('invalid ZIP with letters', () => {
10  expect(isValidZipCode('12a45')).toBe(false);
11});
12
13test('invalid ZIP with too few digits', () => {
14  expect(isValidZipCode('1234')).toBe(false);
15});
16
17test('invalid ZIP+4 with missing dash', () => {
18  expect(isValidZipCode('123456789')).toBe(false);
19});
20
21test('invalid ZIP+4 with wrong digit count', () => {
22  expect(isValidZipCode('12345-678')).toBe(false);
23});