CUSIP Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching cusip, ported and verified for JavaScript. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. 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

// CUSIP
// ReDoS-safe | RegexVault — Finance > Securities & Trading

const cusipRegex = /^[0-9A-Z]{5}[0-9A-Z]{3}[0-9]$/;

function validateCusip(input: string): boolean {
  return cusipRegex.test(input);
}

// Example
console.log(validateCusip("037833100")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Securities & Trading 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

Structure: 6-char issuer code + 2-char issue number + 1 check digit. The issuer code identifies the company; the issue number identifies the specific security class. Check digit uses a weighted Luhn-like algorithm.