Node.js

Modules Commands

Understand Node.js module systems — CommonJS (require) and ES Modules (import). Learn module resolution, creating packages, and migrating between module systems.

5 commands

Pro Tips

Use 'type: "module"' in package.json to enable ESM by default. Use .cjs extension for CommonJS exceptions.

Debug module resolution with 'NODE_DEBUG=module node app.js' to see exactly which files Node tries to load.

Use the 'exports' field in package.json to control which files are importable from your package.

Common Mistakes

You cannot require() an ES module. Use dynamic import() instead: 'const mod = await import("esm-package")'.

Circular dependencies in CommonJS return partially loaded modules. Refactor to break the cycle.

Commands

Preload module

$ node -r dotenv/config app.js

Preload CommonJS module before main.

Import ES module

$ node --import ./setup.js app.js

Preload ES module at startup.

Run as ES module

$ node --input-type=module -e "import fs from 'fs'"

Treat eval/stdin as ES module.

Allow require(ESM)

$ node --experimental-require-module app.js

Allow require() for ES modules (Node.js 22+).

Run TypeScript directly

$ node --experimental-strip-types app.ts

Execute TypeScript without transpiling (Node.js 22+, 2026).