How to Export Module in Node.js: Simple Guide

In Node.js, you export a module by assigning the object, function, or value you want to share to module.exports. Alternatively, you can add properties to exports as a shortcut to export multiple items.

Syntax

Use module.exports to export a single item like a function or object. Use exports to add multiple properties or functions to export. Both are objects representing what your module shares with other files.

• module.exports = value; exports one value.
• exports.name = value; adds named exports.

javascript

module.exports = value;

// or

exports.name = value;

Example

This example shows how to export a function and an object from a module, then import and use them in another file.

javascript

// file: mathUtils.js
function add(a, b) {
  return a + b;
}

const constants = {
  pi: 3.14159
};

module.exports = {
  add,
  constants
};

// file: app.js
const mathUtils = require('./mathUtils');

console.log(mathUtils.add(2, 3)); // 5
console.log(mathUtils.constants.pi); // 3.14159

Output

5
3.14159

Common Pitfalls

A common mistake is mixing module.exports and exports incorrectly. exports is a shortcut to module.exports, but if you assign a new value directly to exports, it breaks the link and nothing gets exported.

Always assign to module.exports when exporting a single item. Use exports.property only to add properties.

javascript

// Wrong way - breaks export
exports = function() {
  console.log('Hello');
};

// Right way
module.exports = function() {
  console.log('Hello');
};

Quick Reference

Remember these tips when exporting modules in Node.js:

• Use module.exports to export a single value.
• Use exports.name = value to export multiple named items.
• Do not assign directly to exports alone.
• Require modules with require('./moduleName').

Key Takeaways

Use module.exports to export a single function, object, or value from a Node.js module.

Use exports.property to add multiple named exports without overwriting module.exports.

Never assign directly to exports alone, as it breaks the export link.

Import exported modules using require('./moduleName') to access their contents.

Keep exports consistent to avoid unexpected undefined imports.