Market Identifier Code (MIC) Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching market identifier code (mic), 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

// Market Identifier Code (MIC)
// ReDoS-safe | RegexVault — Finance > Securities & Trading

const marketIdentifierCodeMicRegex = /^(?!NYSE$)[A-Z0-9]{4}$/;

function validateMarketIdentifierCodeMic(input: string): boolean {
  return marketIdentifierCodeMicRegex.test(input);
}

// Example
console.log(validateMarketIdentifierCodeMic("XNYS")); // 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

ISO 10383 MICs: XNYS=NYSE, XNAS=NASDAQ, XLON=LSE, XTKS=TSE Tokyo, XHKG=Hong Kong, XSES=SGX Singapore. The X prefix denotes the primary/regulated market. S prefix for segments.