# Create User-Defined Modules

Published 2022-12-03

This tutorial explains to you how to create your own module in Node.js. This article provides you with an example as well.

A Node.js Module is a library of functions that could be used in Node.js. These modules are generally small and include functionalities related to a domain. For the list of Node.js modules, you can go here.

There are 3 module type in Node.js:

  • Built-in modules (provided by Node.js installation)
  • User-defined modules (created by the user)
  • Third party modules (generally available on the Internet)

Here are the steps for creating a User-defined module:

1) Create a .js file which contains the Custom module:

// Returns addition of two numbers
exports.add = function (a, b) {
    return a+b;
// Returns difference of two numbers
exports.subtract = function (a, b) {
    return a-b;
  1. Create the main application which calls the User-Defined (Custom) Module:
var cm = require('./customModule');
var a=100, b=10;
console.log("Addition : "+cm.add(a,b));
console.log("Subtraction : "+cm.subtract(a,b));
console.log("My Application has been finished !");

Here are the files we have created:

And here is the execution of the main application: