esm-loader-typescript/README.md

Chainable ESModule Loader for Typescript

# esm-loader-typescript

[Node.js ESModule Loader][node-loaders] for importing and loading
Typescript (`.ts`) files and transpiling on the fly.

**Warning!** Using experimental Node.js features and flags,
API will likely change. This may be helpful for development and testing,
but should not be used in production.

## Usage

```sh
npm install --save-dev esm-loader-typescript
```

We want to import a `.ts` file with Node.js:

```ts
// index.ts
const words: string = 'hello'
console.log(words)
// 'hello'
```

### Standalone

```sh
# node >= 20.7
cat << EOF > ./register.js
import { register } from 'node:module'
register('esm-loader-typescript', import.meta.url)
EOF
NODE_OPTIONS="--import ./register.js" node index.ts

# node < 20.7
NODE_OPTIONS="--loader esm-loader-typescript" node index.ts
```

### Chainable

This loader can be configured, and chained with other loaders, using
[node-esm-loader][node-esm-loader].

```sh
npm install --save-dev node-esm-loader
```

```js
// .loaderrc.js
export default {
  loaders: ['esm-loader-typescript'],
}
```

```sh
# node >= 20.7
NODE_OPTIONS="--import node-esm-loader/register" node index.ts

# node < 20.7
NODE_OPTIONS="--loader node-esm-loader" node index.ts
```

#### Options

##### Config

You may specify a custom TypeScript config filename to use:

```js
// .loaderrc.js
export default {
  loaders: [
    {
      loader: 'esm-loader-typescript',
      options: {
        config: 'tsconfig-custom.json',
      },
    },
  ],
}
```

Otherwise, if a `tsconfig.json` file is found, it will be loaded and used.

##### Debug

```js
// .loaderrc.js
export default {
  loaders: [
    {
      loader: 'esm-loader-typescript',
      options: {
        debug: true,
      },
    },
  ],
}
```

## Related

- [esm-loader-import-relative-extension][esm-loader-import-relative-extension]

## License

[MIT][mit-license]

[esm-loader-import-relative-extension]: https://github.com/brev/esm-loaders/tree/main/packages/esm-loader-import-relative-extension#readme
[mit-license]: https://mit-license.org/
[node-esm-loader]: https://github.com/sebamarynissen/node-esm-loader#readme
[node-loaders]: https://nodejs.org/api/esm.html#loaders