Node.js ES Modules

Node.js ES Modules (ESM)

Node.js supports two module systems:

1. CommonJS (CJS) → uses require() & module.exports

2. ES Modules (ESM) → uses import & export

ES Modules are the modern JavaScript module standard, used in browsers and modern Node.js apps.

⭐ Why Use ES Modules?

✔ Cleaner syntax
✔ Works in both Node.js and browsers
✔ Supports tree-shaking (remove unused code)
✔ Better for large applications
✔ Future standard of JavaScript

1️⃣ Enabling ES Modules in Node.js

You can enable ES module support in two ways:

Option 1: Add "type": "module" in package.json

Then you can use:

• .js for ESM code

• import / export syntax

Option 2: Use .mjs extension

Files ending with .mjs are treated as ES modules automatically.

2️⃣ Exporting in ES Modules

You can export:

• default values

• named values

• functions

• objects

• classes

✅ Named Exports

file: math.js

Importing named exports:

✅ Default Export

file: user.js

Importing default export:

⚠ You can have only one default export per file.

✅ Mixing Default + Named Exports

person.js

Importing:

3️⃣ Exporting Everything at Once

file: utils.js

4️⃣ Importing Everything

5️⃣ ES Module Features

🚀 Top-level Await (No async function needed)

Works only in ES modules, not in CommonJS.

🚀 Strict Mode by Default

ESM automatically uses "use strict";
No need to declare it manually.

🚀 No require(), use import() instead

Example: dynamic import:

6️⃣ Differences Between CommonJS and ES Modules

7️⃣ When to Use ES Modules?

Use ESM when:

✔ working with modern JavaScript
✔ building frontend + backend together
✔ using tools like Babel, Vite, Webpack
✔ wanting cleaner and future-proof syntax

8️⃣ Quick Example Project

math.js

app.js

package.json

Run: