How to create nested modules – Node JS

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In this article, we are going to teach you, how you can have nested modules in your Node JS project. Nested modules help in splitting a large code-base into smaller files. This helps in debugging and scaling easily.

Video tutorial

Let’s say that you want to access the following URL:

http://localhost:3000/users/social

You want to have a “users” module where all user code will go. And you want the user’s module to be further divided into “social” module where all the code for user’s social networks will go, for example.

If you do not know how to create and set up a Node JS application, please check our this tutorial first.

So we will start by creating a user module. Create a new folder named “modules” at the root of your project. Then in this folder, create a file named “users.js”. The following code will go in the users.js file.

const express = require("express")

// [include social.js module]

module.exports = {
	init: function (app) {
		const userRouter = express.Router()

		userRouter.get("/", function (request, result) {
			result.send("Inside users.js")
		})

		app.use("/users", userRouter)

		// [call init method of social.js here]
	}
}

It creates a router object, named userRouter, from the express object. Then it tells the app to use this userRouter object for every route starting from “/users” in the URL. The init function accepts an app object which we will send from our main “server.js” file.

So go to your main “server.js” file and include the users module in it by writing the following line at the top.

const users = require("./modules/users")

const express = require("express")
const app = express()

Then, we need to call the init function of it and pass the app instance to it.

users.init(app)

If you access the following URL now, you will see a message “Inside users.js” in the browser:

http://localhost:3000/users

Now we need to create another file named “social.js” inside modules folder. The following will be the code for social.js file:

const express = require("express")

module.exports = {
	init: function (userRouter) {
		const socialRouter = express.Router()

		socialRouter.get("/", function (request, result) {
			result.send("Inside social.js")
		})

		userRouter.use("/social", socialRouter)
	}
}

This module’s init method accepts userRouter as an argument that we had created in our “users.js” file. And it is using that userRouter object instead of app object because this module will be used only when the “/social” path is appended after the “/users” path.

The final thing you need to do is to call the init method of the “social.js” file inside our “users.js” file. So go to your “users.js” file and first include the social module in it. Write the following line in the [include social.js module] section:

const social = require("./social")

Then write the following code in the [call init method of social.js here] section:

social.init(userRouter)

So if you access the following URL now, you will be able to see “Inside social.js” in your browser.

http://localhost:3000/users/social

We created an E-commerce application in Node JS and Mongo DB where we used nested modules to have admin > products and orders. You can check that project from here.

So that’s how you can have nested modules in Node JS express framework. If you face any problems in following this, kindly do let me know.

Source code – How to create nested modules in Node JS

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