Node ES Modules

Node.js ES Modules (ECMAScript Modules)

Historically, Node.js relied exclusively on the CommonJS module system (require and module.exports). However, as JavaScript evolved, a newer, standardized module system was introduced to the web browser: ES Modules (or ECMAScript Modules).

Today, Node.js fully supports ES Modules natively. This allows you to write back-end JavaScript code using the exact same import and export syntax that you use in front-end frameworks like React, Vue, or vanilla browser JavaScript!

1. How to Enable ES Modules in Node.js

By default, Node.js still treats .js files as CommonJS modules. To start using ES Modules in your project, you have two primary options:

Option A: The .mjs Extension

You can change the file extension of your JavaScript files from .js to .mjs. Node.js will automatically treat any .mjs file as an ES Module.

Option B: Using package.json (Recommended)

If you want your entire project to use ES Modules by default, you can add a specific property to your project's package.json file:

{
  "name": "my-node-app",
  "type": "module"
}

Once "type": "module" is set, all .js files in your project are parsed as ES Modules.

2. Exporting with ES Modules

Unlike CommonJS which uses module.exports, ES Modules use the export keyword. You can export items in two ways: Named Exports and Default Exports.

Named Exports

You can export multiple variables or functions from a single file by placing the export keyword in front of them.

// Exporting individually
export const pi = 3.14159;

export function calculateArea(radius) {
  return pi * radius * radius;
}

Default Exports

A file can have a maximum of one default export. This is typically used when a module only has one primary function or class to share.

function logMessage(msg) {
  console.log(`[LOG]: ${msg}`);
}

// Exporting as default
export default logMessage;

3. Importing with ES Modules

To bring exported code into another file, you use the import keyword.

Important Note: When using ES Modules in Node.js, you must include the .js file extension in your import path for local files!

// 1. Importing Named Exports (must use curly braces and exact names)
import { pi, calculateArea } from './utils.js';

// 2. Importing a Default Export (no curly braces, name it whatever you want)
import myLogger from './logger.js';
// 3. Importing a Built-in Core Module (no relative path needed)
import fs from 'fs';
myLogger("Starting application...");
console.log("Area of circle with radius 5:", calculateArea(5));

4. CommonJS vs. ES Modules Recap

Here is a quick cheat sheet to help you remember the differences: