Docker Environment Variable Assignment Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching docker environment variable assignment, 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

// Docker Environment Variable Assignment
// ReDoS-safe | RegexVault — Dev & Systems > Docker

const dockerEnvironmentVariableAssignmentRegex = /^([a-zA-Z_][a-zA-Z0-9_]{0,255})(?:=([^\x00-\x1F\x7F]*))?$/;

function validateDockerEnvironmentVariableAssignment(input: string): boolean {
  return dockerEnvironmentVariableAssignmentRegex.test(input);
}

// Example
console.log(validateDockerEnvironmentVariableAssignment("NODE_ENV=production")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Docker 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

Variable names must start with a letter or underscore. A bare KEY without = passes the variable from the host environment. Capture group 1 = key, group 2 = value (optional).