esm-loader-import-relative-extension

Node.js ESModule Loader for changing or adding file extensions on relative imports, allowing Node.js to actually resolve the file.

You can use this for .js files, or Node has a built-in flag --experimental-specifier-resolution=node which may work instead. For any file extensions other than .js, this is the loader for you.

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

For example: When using Typescript, the imports of other Typescript files are suggested to not use any file extension, or also just use .js:

// lib.ts
const result: Record<string, string> = {
  welcome: 'hello',
}
export default result.welcome

// index.ts
import welcome from './lib' // tsc will add extension
import welcome from './lib.js' // tsc finds the right file anyway
console.dir(welcome) // 'hello'

However, if we are using ESM loaders with Node.js, the above will fail since Node has no idea what those filenames are. Using our loader, we'll add/modify wanted file extensions to these imports on-the-fly, allowing Node to resolve the file after all.

Chainable

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

npm install --save-dev \
  esm-loader-import-relative-extension \
  esm-loader-typescript \
  node-esm-loader

// .loaderrc.js
export default {
  loaders: [
    'esm-loader-typescript',
    {
      loader: 'esm-loader-import-relative-extension',
      options: {
        extensions: {
          '.ts': {
            '': '.ts',
            '.js': '.ts',
          },
        },
      },
    },
  ],
}

Options

Extensions

With the options below, any relative imports found inside .ts files, which are either missing a file extension, or have a .js extension, will be rewritten on-the-fly to have a .ts extension instead:

// .loaderrc.js
export default {
  loaders: [
    {
      loader: 'esm-loader-import-relative-extension',
      options: {
        extensions: {
          '.ts': {
            '': '.ts'
            '.js': '.ts',
          },
        },
      },
    },
  ],
}

Debug

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

Ordering

In your loader chain:

• This loader should come after:
  • esm-loader-import-alias

License

MIT