CommonJS is the original module system in Node.js. Each file is a module. You export values with module.exports and import them with require().
CommonJS modules are loaded synchronously, which is fine for server-side code.
Node.js
Beginner
9 min read
CommonJS Modules (require / exports)
Example
// --- math.js (exporting) ---
function add(a, b) {
return a + b;
}
function subtract(a, b) {
return a - b;
}
const PI = 3.14159;
// Export an object with multiple values:
module.exports = { add, subtract, PI };
// --- app.js (importing) ---
const { add, subtract, PI } = require('./math');
console.log(add(10, 5)); // 15
console.log(subtract(10, 5)); // 5
console.log(PI); // 3.14159
// Import a single default export:
// module.exports = function greet(name) { ... };
// const greet = require('./greet');
// Built-in modules use the same require() syntax:
const path = require('path');
const os = require('os');
console.log(path.join(__dirname, 'files', 'data.txt'));
console.log(os.homedir());