feat: CJS dual-publish

[tzezar]

feat: CJS dual-publish

Labels: enhancement, roadmap

---

Summary

Publish both ESM and CommonJS builds to support older Node.js projects that haven't migrated to ESM yet.

Problem

throtto is ESM-only ("type": "module"). Projects using require() can't import it without dynamic import() workarounds. This excludes:

• Older Express/Fastify apps
• Some test frameworks with CJS-only configs
• Enterprise codebases locked to CJS
• AWS Lambda with older Node.js runtimes

Proposed solution

Use tsup dual output:

// tsup.config.ts
export default defineConfig({
  format: ['esm', 'cjs'],
  // ...
})

Update package.json exports with conditional exports:

{
  "exports": {
    ".": {
      "types": "./dist/index.d.ts",
      "import": "./dist/index.js",
      "require": "./dist/index.cjs"
    }
  }
}

Considerations

• Increases package size (~2x dist)
• Need to test CJS output doesn't break tree-shaking for ESM consumers
• .d.cts type files may be needed
• All 40+ entry points need dual exports

Alternative: document ESM-only stance

If dual-publish is too much maintenance, clearly document:

• How to use throtto in CJS projects via dynamic import()
• Minimum Node.js version for native ESM support
• Link to migration guides

Acceptance criteria

• Decide: dual-publish or document ESM-only
• If dual: update tsup config, all package.json exports, test CJS output
• If ESM-only: add clear docs with workaround examples