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How to Create Index.js File in Node?

05th Sep, 2023
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    How to Create Index.js File in Node?

    For a long time, JavaScript has only been thought of as a client-side programming language. But the introduction of Node.js, a JavaScript runtime environment capable of executing JavaScript codes outside of the browser changed the game. 

    Node.js is now an essential part of building modern applications in the JavaScript ecosystem. Frontend frameworks such as React, Vue, Angular, and React Native use Node.js under the hood for building fast and scalable applications. Check here for Node.js certification cost and get started! 

    Getting to know how Node.js is used to build backend applications is something that you must do to establish yourself in the JavaScript world. 

    In this article, you will learn how to create an index.js file using Node, node index.js command, and examples. So, if you're ready, then let's jump into the tutorial... 

    What is Node Index.js?

    What's Node.js, it is a cross-platform back-end JavaScript runtime environment that runs on the V8 engine and executes JavaScript code outside the browser. 

    What about node Index.js? Index of Node.js is the file that runs initially once the Node.js code is executed. 

    It is responsible for your application's startup, routing, and other functions. Other modules, such as Express, Mongoose, Axios, and others, are used in adding functionalities to a Node.js app. 

    Create Index.js In Node

    When you visit most domains, the index files are the first to be served. For instance, visiting the homepage of an HTML or PHP site will take you to the index file. The same concept is used with Node.js, but in Node, using index.js is optional. You can always change the name to something else, such as main.js or app.js instead. All you need to do is make the necessary references in the routing component. 

    It is simple to create an Index.js file in Node.js. To create your first Nodejs index file, follow the steps below. 

    Here are the steps that you’ll follow to create an index.js file: 

    • Head to the Node.js website, download, and install the node package file. 
    • Create a new project folder in your working directory. 
    • Navigate to the project's location on your terminal and run npm init -y. The above command will produce a package.json file with the codes below inside of it.
      "name": "nodejs", 
      "version": "1.0.0", 
      "description": "", 
      "main": "index.js", 
      "scripts": { 
        "test": "echo \"Error: no test specified\" && exit 1" 
      "keywords": [], 
      "author": "", 
      "license": "ISC" 
    • Open the project on a code editor such as sublime or vs code. 
    • Create an index.js file inside your project folder. 
    • Paste the codes below within the index.js file. 
    const http = require("http"); 
    //create a server object: 
      .createServer(function (req, res) { 
        res.write("<h1>Hello World!</h1>");  
        //write a response to the client 
        //end the response 
    //Server runs on localhost:8080 
    • Run your server on the terminal using node index.js.  
    • Visit your browser on localhost:8080. 

    Node.js includes an HTTP module that allows you to create a server and serve content to a specific address. We simply created a web server in the code above that writes a heading tag of "Hello World" to the screen and serves it to the localhost:8080 address. When the above code is run through a browser, it yields the following result. 

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    Node Index.js: Usage

    Using Node.js is easy, let's demonstrate its usage by building a simple website that has three pages. The index page, about, and sitemap pages to be precise. 

    Example 1: Building a simple website

    Follow the steps below to build a simple website using Node.js, we will be including the CSS which will be imported from a content delivery network (CDN). 

    Step 1: 

    Create a new project folder and run the code below via the terminal. Make sure you change your directory to this project folder. 

    npm init -y 

    Step 2: 

    Install Express, a Node.js web application framework that offers many features for building web and mobile applications. 

    npm install --save express 

    Step 3: 

    Copy and paste the codes below inside the index.js file. 

    // Import essential libraries 
    const express = require('express'); 
    const app = express(); 
    const path = require('path'); 
    const router = express.Router(); 
    // Setup essential routes 
    router.get('/', function(req, res) { 
        res.sendFile(path.join(__dirname + '/index.html')); 
        //__dirname : It will resolve to your project folder. 
    router.get('/about', function(req, res) { 
        res.sendFile(path.join(__dirname + '/about.html')); 
    router.get('/sitemap', function(req, res) { 
        res.sendFile(path.join(__dirname + '/sitemap.html')); 
    //add the router 
    app.use('/', router); 
    app.listen(process.env.port || 3000); 
    console.log('Running at Port 3000'); 

    The router object was gotten from the Express framework we recently installed. It lets us specify which location we want certain files and codes to execute. 

    Step 4: 

    Create an index.html file and paste the following codes inside. The codes also include a bootstrap CDN link that solves all our CSS styling needs. 

        <title>Express HTML</title> 
        <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script> 
        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css"> 
        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap-theme.min.css"> 
        <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js"></script> 
        <div style="margin:100px;"> 
            class="navbar navbar-inverse navbar-static-top"> 
            <div class="container"> 
                <a class="navbar-brand" href="/">Express HTML</a> 
                <ul class="nav navbar-nav"> 
                    <li class="active"> 
                        <a href="/">Home</a> 
                        <a href="/about">About</a> 
                        <a href="/sitemap">Sitemap</a> 
            <div class="jumbotron" style="padding:40px;"> 
                <h1>Hello, world!</h1> 
                <p>This is a simple hero unit, a simple jumbotron-style component for calling extra attenion to featured content or information.</p> 
                <p><a class="btn btn-primary btn-lg" href="#" role="button">Learn more</a></p> 

    Note that all the CSS classes such as the “btn, btn-primary, btn-lg" are all coming from the imported CSS files. 

    Step 5: 

    Run the code on the terminal using node index.js, then view it on the browser via localhost:3000. See the image below. 

    Example 2: Get web resources using Axios

    Here is another way to use the index.js file in NodeJs. Let’s use Axios to retrieve a bulk of users from the Jsonplaceholder website. 

    NodeJs has a native HTTPS module that can help you make API calls online, but Axios is fantastic, and its usage is effortless. Also, many developers out there use it as their number one package for all things related to making API calls. To use it, follow the steps below: 

    Step 1: 

    Open the terminal on your project directory. 

    Step 2: 

    Run npm install Axios on the terminal to install the package. 

    Step 3: 

    Create an index.js file in the root folder of your project and paste the codes below it. 

    // import axios 
    const axios = require('axios'); 
    // Specify a resource location 
    const resourse = 'https://jsonplaceholder.typicode.com/users'; 
      .then(users => console.log(users)) 
      .catch(error => console.log(error)); 

    Step 4: 

    Run node index.js on your terminal and observe the result, see the image below. 

    Example 3: Building a countdown timer 

    Here is another usage of index.js in Node.js, let’s build a timer to countdown every second starting from 50. 

    let time = 50; 
    let countdown = setInterval(update, 1000); 
    function update() { 
        let min = Math.floor(time / 60); 
        let sec = time % 60; 
        if (min == 0 && sec == 0)        

    Node Index.js: Implementation

    We have one more surprise for you on how to create an index.js in Node.js, and this time it's through a package called create-index. If you want to build an ES6 module package and you want to quickly bundle the files before shipping them online, the `create-index` package will be very helpful to you. How do you use it? Follow the steps below: 

    Step 1: 

    Run npm install create-index to install the package to your project. 

    Step 2: 

    Create an index entry file by running this command npx create-index ./ on the terminal. 

    The above command will create an index.js file and add a line of code as can be seen in the snippet below: 

    // @create-index 

    Step 3: 

    Create the files to be included for export. These files are the once you intend on pushing together as one package. Create them at the root of the project, you write all your logic, classes, and functions in these files. You can use the command below: 

    touch foo.js bar.js baz.js 

    The above code should all be lined up similar to the block below: 

      - bar.js 
      - baz.js 
      - foo.js 
      - index.js 

    Step 4: 

    Bundle them up by running npx create-index ./ once again on the terminal, and you will have a result similar to the one in the image below. 

    How to Ignore Files on –update

    For many reasons, you may want to exclude some files from being listed in the index.js file. To achieve this, change the comment on the index.js file to the one seen in the block below: 

    //  @create-index {"ignore": ["/baz.js$/"]} 

    Next, run npx create-index --update ./index.js on the terminal and the result should look like the one below: 

    And there you have it with how to create an index.js in Node.js. 

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    We have come to the end of this tutorial, hopefully, you got some understanding of how to create index.js files in Node.js. We have a ton more tutorials like this one on KnowledgeHut. Check for KnowledgeHut’s Node.js certification cost and learn Node or even brush up your skills while earning certification. 

    Frequently Asked Questions (FAQs)

    1How Can I Run Index.js File in Node?

    On the project directory, simply run node index.js on the terminal to execute the file and ensure that your terminal is pointed to the same location as the index file. 

    2What's Index.js in Node?

    An index.js file is called an entry file for a Node.js application. When a server is started with Node, it defaults to the index.js file, except it is reconfigured. 

    3How Can I Write Node.js Module?

    There are many ways to write a Node.js module, but for simplicity and automation, you can use the create-index npm package. 

    4What's the Process to Create a Node.js File?

    Once the create-index package is installed on your project, simply running npx create-index ./ on the terminal will create an index.js file for you. 


    Bala Krishna Ragala

    Blog Author

    Bala Krishna Ragala, Head of Engineering at upGrad, is a seasoned writer and captivating storyteller. With a background in EdTech, E-commerce, and LXP, he excels in building B2C and B2B products at scale. With over 15 years of experience in the industry, Bala has held key roles as CTO/Co-Founder at O2Labs and Head of Business (Web Technologies) at Zeolearn LLC. His passion for learning, sharing, and teaching is evident through his extensive training and mentoring endeavors, where he has delivered over 80 online and 50+ onsite trainings. Bala's strengths as a trainer lie in his extensive knowledge of software applications, excellent communication skills, and engaging presentation style.

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