French Code Postal Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching french code 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

// French Code Postal
// ReDoS-safe | RegexVault — Localization > Postal Codes

const frenchCodePostalRegex = /^(0[1-9]|[1-8][0-9]|9[0-8])[0-9]{3}$/;

function validateFrenchCodePostal(input: string): boolean {
  return frenchCodePostalRegex.test(input);
}

// Example
console.log(validateFrenchCodePostal("75001")); // 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

French department codes run 01-95 (metropolitan), 97 (overseas departments: 971=Guadeloupe, 972=Martinique, 973=French Guiana, 974=Réunion, 976=Mayotte). 99 is excluded (reserved). Paris arrondissements are 75001-75020.