Spanish Código Postal Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching spanish código postal, 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

// Spanish Código Postal
// ReDoS-safe | RegexVault — Localization > Postal Codes

const spanishCdigoPostalRegex = /^(0[1-9]|[1-4][0-9]|5[0-2])[0-9]{3}$/;

function validateSpanishCdigoPostal(input: string): boolean {
  return spanishCdigoPostalRegex.test(input);
}

// Example
console.log(validateSpanishCdigoPostal("28001")); // 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

Spanish province codes 01-52. Madrid is 28, Barcelona is 08. Ceuta is 51, Melilla is 52. The Canary Islands (Gran Canaria 35, Tenerife 38) are Spanish territory.