Dockerfile FROM Instruction Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching dockerfile from instruction, 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

// Dockerfile FROM Instruction
// ReDoS-safe | RegexVault — Dev & Systems > Docker

const dockerfileFromInstructionRegex = /^FROM\s+(?:--platform=[^\s]+\s+)?([a-z][a-z0-9\-._\/]*(?::[a-zA-Z0-9._\-]+|@sha256:[a-fA-F0-9]{64})?)(?:\s+AS\s+([a-zA-Z][a-zA-Z0-9_\-]*))?$/i;

function validateDockerfileFromInstruction(input: string): boolean {
  return dockerfileFromInstructionRegex.test(input);
}

// Example
console.log(validateDockerfileFromInstruction("FROM nginx")); // 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

Group 1 = image reference, group 2 = AS alias. Multi-stage builds use FROM...AS extensively. 'scratch' is a special minimal base image. --platform enables cross-platform builds.