esm-loader

Node.js import hook to instantaneously transform TypeScript to ESM on demand using esbuild.

Features

Transforms TypeScript to ESM on demand
Supports TS extensions .cjs & .mjs (.cts & .mts)
Classic Node.js resolution (extensionless & directory imports)
Cached for performance boost
Supports Node.js v12.20.0+
Handles node: import prefixes

Tip:

esm-loader doesn't hook into require() calls.

Use this with cjs-loader for require() support. Alternatively, use tsx to handle them both automatically.

Install

npm install --save-dev @esbuild-kit/esm-loader

Usage

Pass @esbuild/esm-loader into the --loader flag.

node --loader @esbuild/esm-loader ./file.ts

TypeScript configuration

The following properties are used from tsconfig.json in the working directory:

jsxFactory
jsxFragmentFactory

Cache

Modules transformations are cached in the system cache directory (TMPDIR). Transforms are cached by content hash so duplicate dependencies are not re-transformed.

Set environment variable ESBK_DISABLE_CACHE to a truthy value to disable the cache:

ESBK_DISABLE_CACHE=1 node --loader @esbuild/esm-loader ./file.ts

FAQ

Can it import JSON modules?

Yes. This loader enables importing native JSON modules.

Can it import ESM modules over network?

Node.js has built-in support for network imports behind the --experimental-network-imports flag.

You can pass it in with esm-loader:

node --loader @esbuild/esm-loader --experimental-network-imports ./file.ts

Can it resolve files without an extension?

In ESM, import paths must be explicit (must include file name and extension).

For backwards compatibility, this loader adds support for classic Node resolution for extensions: .js, .json, .ts, .tsx, .jsx. Resolving a index file by the directory name works too.

import file from './file' // -> ./file.js
import directory from './directory' // -> ./directory/index.js

tsx - Node.js runtime powered by esbuild using @esbuild-kit/cjs-loader and @esbuild-kit/esb-loader.
@esbuild-kit/cjs-loader - TypeScript & ESM to CJS transpiler using the Node.js loader API.

bushuai/esm-loader