INI File Key=Value Pair Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching ini file key=value pair, 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

// INI File Key=Value Pair
// ReDoS-safe | RegexVault — Dev & Systems > Config

const iniFileKeyvaluePairRegex = /^([a-zA-Z_][a-zA-Z0-9_.\-]{0,254})\s*[=:]\s*([^;#\n]*)\s*(?:[;#].*)?$/m;

function validateIniFileKeyvaluePair(input: string): boolean {
  return iniFileKeyvaluePairRegex.test(input);
}

// Example
console.log(validateIniFileKeyvaluePair("host=localhost")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Config 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

Groups: 1=key, 2=value (trailing whitespace and inline comment stripped). Both = and : are valid delimiters (Python configparser accepts both). git config uses = only.