dylang / cjs-loader

Node.js loader for compiling ESM & TypeScript modules to CommonJS

cjs-loader

Node.js require() hook to instantaneously transform ESM & TypeScript to CommonJS on demand using esbuild.

Features

• Transforms ESM & TypeScript to CommonJS on demand
• Supports TS extensions .cjs & .mjs (.cts & .mts)
• Cached for performance boost
• Supports Node.js v12.16.2+
• Handles node: import prefixes
• Resolves tsconfig.json paths

Tip:

cjs-loader doesn't hook into dynamic import() calls.

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

Install

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

Usage

Pass @esbuild/cjs-loader into the --require flag

node -r @esbuild/cjs-loader ./file.js

TypeScript configuration

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

• jsxFactory
• jsxFragmentFactory

Custom tsconfig.json path

By default, tsconfig.json will be detected from the current working directory.

To set a custom path, use the ESBK_TSCONFIG_PATH environment variable:

ESBK_TSCONFIG_PATH=./path/to/tsconfig.custom.json node -r @esbuild/cjs-loader ./file.js

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 -r @esbuild/cjs-loader ./file.js

Related

• tsx - Node.js runtime powered by esbuild using @esbuild-kit/cjs-loader and @esbuild-kit/esm-loader.

• @esbuild-kit/esm-loader - TypeScript to ESM transpiler using the Node.js loader API.