Australian Postcode Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching australian 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

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

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

function validateAustralianPostcode(input: string): boolean {
  return australianPostcodeRegex.test(input);
}

// Example
console.log(validateAustralianPostcode("2000")); // 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

Australian postcode ranges by state: NSW/ACT 2000-2999, VIC 3000-3999, QLD 4000-4999, SA 5000-5999, WA 6000-6999, TAS 7000-7999, NT 0800-0999. Leading zeros (NT/ACT) require string storage.