How to Export Function in Node.js: Simple Guide

In Node.js, you export a function by assigning it to module.exports or adding it as a property to exports. This makes the function available to other files when you use require().

Syntax

To export a function in Node.js, you use either module.exports or exports. module.exports replaces the entire export object, while exports adds properties to the existing export object.

• module.exports = functionName; exports a single function.
• exports.functionName = functionName; exports a named function as a property.

javascript

module.exports = functionName;

// or

exports.functionName = functionName;

Example

This example shows how to export a function named greet and use it in another file.

javascript

// greet.js
function greet(name) {
  return `Hello, ${name}!`;
}

module.exports = greet;

// app.js
const greet = require('./greet');
console.log(greet('Alice'));

Output

Hello, Alice!

Common Pitfalls

A common mistake is mixing exports and module.exports. Assigning a new value to exports alone does not change the exported module. Always use module.exports to export a single function or object.

javascript

// Wrong way:
exports = function() {
  console.log('This will NOT be exported');
};

// Right way:
module.exports = function() {
  console.log('This will be exported');
};

Quick Reference

Method	Usage	Notes
module.exports = functionName;	Exports a single function or object	Replaces entire export object
exports.functionName = functionName;	Exports multiple named functions	Adds properties to exports object
exports = functionName;	Does NOT export function	Overrides local exports variable only

Key Takeaways

Use module.exports to export a single function or object in Node.js.

Use exports to add multiple named exports as properties.

Never assign directly to exports alone; it won't change the exported module.

Require the exported function in another file using require('./filename').

Remember module.exports replaces the export object, exports adds to it.