Packlets are a nice way to keep your JavaScript codebase somewhat loosely-coupled, without having to separate things into different npm packages.

You follow these 5 rules:

1. Packlets live in ./src/packlets/<name>/ and the entry point is index.ts.

2. Files outside a packlet can only import from packlet’s entry point, index.ts.

3. Files inside a packlet may not import its own entry point, index.ts.

4. Packlets can import other packlets but cannot create circular dependencies.

5. Packlets can only import other packlets and npm packages.

There is an ESLint plugin to enforce these rules.

Setting up a project for packlets:

mkdir -p src/packlets
yarn add --dev @rushstack/eslint-plugin-packlets

Then in .eslintrc, add "plugin:@rushstack/eslint-plugin-packlets/recommended" to the extends section.