@jjuidev/esm-package-json

A utility CLI tool that automatically generates a minimal package.json file with "type": "module" in your dist/esm folder to ensure proper ESM module resolution.

Installation

Global Installation (Recommended)

npm install -g @jjuidev/esm-package-json

Local Installation

npm install --save-dev @jjuidev/esm-package-json

Usage

CLI Usage

After building your TypeScript project, run:

esm-package-json

Or specify a custom dist folder:

esm-package-json --dist ./build
esm-package-json -d ./output

What it does

This tool scans your dist folder and:

1. Looks for an esm subdirectory
2. Creates a package.json file inside the esm folder if it doesn't exist
3. The generated package.json contains: {"type": "module"}

This ensures that your ESM modules are properly recognized by Node.js and bundlers.

Example

Given this project structure:

your-project/
├── dist/
│   ├── cjs/
│   │   └── index.cjs
│   └── esm/
│       └── index.js
└── package.json

Running esm-package-json will create:

your-project/
├── dist/
│   ├── cjs/
│   │   └── index.cjs
│   └── esm/
│       ├── index.js
│       └── package.json  ← Generated with {"type": "module"}
└── package.json

Options

| Option | Alias | Description | Default | | -------- | ----- | ---------------------------- | -------- | | --dist | -d | Specify the dist folder path | ./dist |

Integration with Build Tools

With tsup

Add to your package.json scripts:

{
	"scripts": {
		"build": "tsup",
		"postbuild": "esm-package-json"
	}
}

With npm scripts

{
	"scripts": {
		"build": "tsc && esm-package-json",
		"build:watch": "tsc --watch & esm-package-json --dist ./dist"
	}
}

Why do you need this?

When building dual-package libraries (both CommonJS and ESM), you often have separate output folders:

• dist/cjs/ for CommonJS files
• dist/esm/ for ESM files

Node.js determines module type based on the nearest package.json file. Without a package.json with "type": "module" in the ESM folder, Node.js might not correctly identify your ESM modules, leading to import/export issues.

Requirements

• Node.js >= 16.0.0

Repository

• GitHub: https://github.com/jjuidev/esm-package-json
• Issues: https://github.com/jjuidev/esm-package-json/issues

License

MIT © jjuidev

Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Changelog

1.0.0

• Initial release
• CLI tool to generate ESM package.json files
• Support for custom dist folder paths