# Developing `hello-world` (ESM) Summary

## Minimal Layout
- `package.json`, `README.md`, `src/index.js` (ESM only).
- `package.json` uses `"type": "module"` and explicit `exports`.
- `files` allow-list to control shipped content.

Example `package.json`:
```json
{
  "name": "hello-world",
  "version": "1.0.0",
  "type": "module",
  "exports": {
    ".": "./src/index.js"
  },
  "files": ["src", "README.md", "package.json"],
  "engines": {
    "node": ">=18"
  }
}
```

Example `src/index.js`:
```js
export function helloWorld() {
  console.log("Hello World!!!");
}
```

## Sub-modules (Subpath Exports)
- Expose sub-modules using explicit subpaths in `exports`.
- Keep public API small and intentional.

Example:
```json
{
  "exports": {
    ".": "./src/index.js",
    "./greetings": "./src/greetings.js",
    "./callouts": "./src/callouts.js"
  }
}
```

## `exports` vs `files`
- `exports` defines the public import surface (what consumers can import).
- `files` defines what gets packaged; supports globs and negation.

Example:
```json
{
  "files": ["dist/**", "README.md", "!dist/**/*.map"]
}
```

## Dev Workflow (Separate Repo, Live Updates)
- Use `npm link` for live-edit development across repos.

Publisher repo:
```bash
npm link
```

Consumer repo:
```bash
npm link hello-world
```

Notes:
- If you build to `dist/`, run a watch build so the consumer sees updates.
- Unlink when done:
```bash
npm unlink hello-world
```

## Distribution as a `.tgz` Artifact
- Create a tarball with `npm pack` and distribute the `.tgz` file.
- Install directly from the tarball path.
- Use `npm pack --dry-run` to verify contents before sharing.
- The `.tgz` is written to the current working directory where `npm pack` is run.
- You can redirect output with `--pack-destination` (or `pack-destination` config).
- Ship `package.json` in the artifact, but exclude `package-lock.json` (keep it in the repo for development only).

Commands:
```bash
npm pack
npm install ./hello-world-1.0.0.tgz
```

Example with output directory:
```bash
npm pack --pack-destination ./artifacts
```