New Zealand Postcode Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching new zealand postcode, ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// New Zealand Postcode
// ReDoS-safe | RegexVault — Localization > Postal Codes

const newZealandPostcodeRegex = /^([0-9]{4})$/;

function validateNewZealandPostcode(input: string): boolean {
  return newZealandPostcodeRegex.test(input);
}

// Example
console.log(validateNewZealandPostcode("0110")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Postal Codes category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

New Zealand postcode ranges: 0100-0999 (Northland), 1010-1072 (Auckland central), 4410-4499 (Taupo), 6011-6099 (Wellington), 8011-8142 (Christchurch), 9016-9999 (Dunedin/Invercargill/Otago). Introduced 2006.