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Chapter XXII · Modules

CommonJS

CommonJS is the traditional module system used in Node.js, relying on `require()` and `module.exports`.

01 How It Works

Think of a traditional server-room supply cabinet unlocked synchronously on request.

CommonJS modules are loaded synchronously at runtime, making them well-suited for server-side Node.js environments.

example.js
// math.js
module.exports = {
  add: (a, b) => a + b
};

// app.js
const math = require('./math.js');

  1. 1. Assign exports to `module.exports` or `exports.property`.

  2. 2. Load dependencies synchronously using `require('./file.js')`.

  3. 3. Execute module code on demand.

02 Practical Example

Here is how you might see this concept applied in real-world code:

practical.js
const fs = require('fs');
fs.readFileSync('file.txt');

Key Takeaway

CommonJS is the classic synchronous module standard historically utilized across Node.js applications.

Related Concepts