{"id":12462,"date":"2024-08-27T10:00:20","date_gmt":"2024-08-27T04:30:20","guid":{"rendered":"https:\/\/www.placementpreparation.io\/blog\/?p=12462"},"modified":"2025-02-27T12:59:00","modified_gmt":"2025-02-27T07:29:00","slug":"node-js-interview-questions-for-freshers","status":"publish","type":"post","link":"https:\/\/www.placementpreparation.io\/blog\/node-js-interview-questions-for-freshers\/","title":{"rendered":"Top Node JS Interview Questions for Freshers"},"content":{"rendered":"

Are you preparing for your first Node.js interview and wondering what questions you might face?<\/p>

Understanding the key Node.js interview questions for freshers can give you more clarity.<\/p>

With this guide, you’ll be well-prepared to tackle these Node.js interview questions and answers for freshers and make a strong impression in your interview.<\/p>

\"fsd<\/a><\/p>

Practice Node JS Interview Questions and Answers<\/h2>

Below are the top 50 Node JS interview questions for freshers with answers:<\/p>

1. How do you create a basic HTTP server in Node.js?<\/h3>

Answer:<\/strong><\/p>

Use the http<\/strong> module to create a server that listens on a specified port and responds to client requests.<\/p>

\n

const http = require(‘http’);
\nconst server = http.createServer((req, res) => {
\nres.statusCode = 200;
\nres.setHeader(‘Content-Type’, ‘text\/plain’);
\nres.end(‘Hello, World!’);
\n});
\nserver.listen(3000);<\/p>\n<\/div><\/div>

2. What is the event loop in Node.js, and how does it handle asynchronous operations?<\/h3>

Answer:<\/strong><\/p>

The event loop in Node.js manages asynchronous operations by executing callbacks when tasks are completed, ensuring non-blocking I\/O operations.<\/p>

3. How do you handle uncaught exceptions in a Node.js application?<\/h3>

Answer:<\/strong><\/p>

Use the process.on(‘uncaughtException’)<\/strong> event to catch and handle uncaught exceptions globally.<\/p>

\n

process.on(‘uncaughtException’, (err) => {
\nconsole.error(‘Uncaught Exception:’, err.message);
\nprocess.exit(1);
\n});<\/p>\n<\/div><\/div>

4. Write a Node.js script that reads the content of a file asynchronously and logs it to the console.<\/h3>

Answer:<\/strong><\/p>

Use the fs.readFile<\/strong> method to read the file content asynchronously and handle the result in a callback.<\/p>

\n

const fs = require(‘fs’);
\nfs.readFile(‘example.txt’, ‘utf8’, (err, data) => {
\nif (err) throw err;
\nconsole.log(data);
\n});<\/p>\n<\/div><\/div>

5. How do you implement a simple promise-based function in Node.js?<\/h3>

Answer:<\/strong><\/p>

Use the Promise<\/strong> constructor to create a function that returns a promise and resolves or rejects based on a condition.<\/p>

\n

function myPromiseFunction(value) {
\nreturn new Promise((resolve, reject) => {
\nif (value) resolve(‘Success’);
\nelse reject(‘Failure’);
\n});
\n}<\/p>\n<\/div><\/div>

6. How do you create and export a custom module in Node.js?<\/h3>

Answer:<\/strong><\/p>

Define the module’s functionality in a separate file and export it using<\/p>

\n

module.exports for use in other files.
\n\/\/ myModule.js
\nmodule.exports = function greet(name) {
\nreturn `Hello, ${name}`;
\n};
\n\/\/ main.js
\nconst greet = require(‘.\/myModule’);
\nconsole.log(greet(‘John’));<\/p>\n<\/div><\/div>

7. What is the difference between require and import in Node.js?<\/h3>

Answer:<\/strong><\/p>

require<\/strong> is used in CommonJS modules, while import<\/strong> is used in ES6 modules. import<\/strong> provides better support for static analysis and tree-shaking.<\/p>

8. How do you install a specific version of an NPM package?<\/h3>

Answer:<\/strong><\/p>

Use npm install<\/strong> followed by the package name and version to install a specific version of an NPM package.<\/p>

\n

npm install express@4.17.1<\/p>\n<\/div><\/div>

9. Write a Node.js script that uses an NPM package to make an HTTP request.<\/h3>

Answer:<\/strong><\/p>

Install the axios<\/strong> package and use it to make a GET request to an external API.<\/p>

\n

const axios = require(‘axios’);
\naxios.get(‘https:\/\/api.example.com\/data’)
\n.then(response => console.log(response.data))
\n.catch(error => console.error(error));<\/p>\n<\/div><\/div>

10. How do you handle dependencies in a Node.js project to avoid version conflicts?<\/h3>

Answer:<\/strong><\/p>

Use a package-lock.json<\/strong> file to lock dependency versions and npm ci<\/strong> to install exact versions from the lock file.<\/p>

11. How do you handle multiple asynchronous operations in Node.js using async\/await?<\/h3>

Answer:<\/strong><\/p>

Use async<\/strong> functions and await<\/strong> to handle asynchronous operations sequentially, improving code readability and error handling.<\/p>

\n

async function fetchData() {
\ntry {
\nconst response = await axios.get(‘https:\/\/api.example.com\/data’);
\nconsole.log(response.data);
\n} catch (error) {
\nconsole.error(error);
\n}
\n}<\/p>\n<\/div><\/div>

12. Write a Node.js function that executes two promises in parallel and returns the combined result.<\/h3>

Answer:<\/strong><\/p>

Use Promise.all<\/strong> to execute multiple promises in parallel and return their results as an array.<\/p>

\n

async function fetchData() {
\nconst [data1, data2] = await Promise.all([
\naxios.get(‘https:\/\/api.example.com\/data1’),
\naxios.get(‘https:\/\/api.example.com\/data2’)
\n]);
\nreturn { data1: data1.data, data2: data2.data };
\n}<\/p>\n<\/div><\/div>

13. How do you convert a callback-based function to a promise-based one in Node.js?<\/h3>

Answer:<\/strong><\/p>

Use util.promisify<\/strong> to convert callback-based functions to return promises, enabling async\/await<\/strong> usage.<\/p>

\n

const fs = require(‘fs’);
\nconst util = require(‘util’);
\nconst readFileAsync = util.promisify(fs.readFile);<\/p>\n

readFileAsync(‘example.txt’, ‘utf8’)
\n.then(data => console.log(data))
\n.catch(err => console.error(err));<\/p>\n<\/div><\/div>

14. How do you handle errors in an async\/await function?<\/h3>

Answer:<\/strong><\/p>

Use a try…catch<\/strong> block to handle errors in async\/await<\/strong> functions, ensuring that errors are properly caught and handled.<\/p>

\n

async function fetchData() {<\/p>\n

try {
\nconst response = await axios.get(‘https:\/\/api.example.com\/data’);
\nconsole.log(response.data);
\n} catch (error) {
\nconsole.error(‘Error fetching data:’, error);
\n}
\n}<\/p>\n<\/div><\/div>

15. Write a Node.js function that uses setTimeout to delay an operation by 2 seconds using a promise.<\/h3>

Answer:<\/strong><\/p>

Wrap setTimeout<\/strong> in a promise to create a delay function that can be awaited in an async<\/strong> function.<\/p>

\n

function delay(ms) {
\nreturn new Promise(resolve => setTimeout(resolve, ms));
\n}<\/p>\n

async function delayedOperation() {
\nawait delay(2000);
\nconsole.log(‘Operation after delay’);
\n}<\/p>\n<\/div><\/div>

16. How do you create a basic Express.js application with a single route?<\/h3>

Answer:<\/strong><\/p>

Use express()<\/strong> to create an app and define a route with app.get<\/strong> that responds to client requests.<\/p>

const express = require(‘express’);
\nconst app = express();<\/p>

app.get(‘\/’, (req, res) => {
\nres.send(‘Hello, Express!’);
\n});
\napp.listen(3000);<\/p>

\n[\/su_note]\n<\/p>

17. What is middleware in Express.js, and how do you use it?<\/h3>

Answer:<\/strong><\/p>

Middleware functions in Express.js process requests before they reach the route handlers, and they can modify the request, response, or end the request-response cycle.<\/p>

\n

app.use((req, res, next) => {
\nconsole.log(`${req.method} ${req.url}`);
\nnext();
\n});<\/p>\n<\/div><\/div>

18. How do you handle form data submission in an Express.js application?<\/h3>

Answer:<\/strong><\/p>

Use the express.urlencoded<\/strong> middleware to parse URL-encoded form data from the request body.<\/p>

\n

app.use(express.urlencoded({ extended: true }));
\napp.post(‘\/submit’, (req, res) => {
\nres.send(`Received: ${req.body.name}`);
\n});<\/p>\n<\/div><\/div>

19. Write an Express.js route that serves static files from a directory.<\/h3>

Answer:<\/strong><\/p>

Use the express.static<\/strong> middleware to serve static files like HTML, CSS, and JavaScript from a public directory.<\/p>

\n

app.use(express.static(‘public’));<\/p>\n<\/div><\/div>

20. How do you implement error handling in an Express.js application?<\/h3>

Answer:<\/strong><\/p>

Define an error-handling middleware function with four parameters (err, req, res, next<\/strong>) to handle errors globally.<\/p>

\n

app.use((err, req, res, next) => {
\nconsole.error(err.stack);
\nres.status(500).send(‘Something broke!’);
\n});<\/p>\n<\/div><\/div>

21. How do you create a RESTful API in Express.js with CRUD operations?<\/h3>

Answer:<\/strong><\/p>

Define routes using GET<\/strong>, POST<\/strong>, PUT<\/strong>, and DELETE<\/strong> methods to perform CRUD operations on resources like users.<\/p>

\n

app.get(‘\/users’, (req, res) => { \/* Fetch users *\/ });
\napp.post(‘\/users’, (req, res) => { \/* Create user *\/ });
\napp.put(‘\/users\/:id’, (req, res) => { \/* Update user *\/ });
\napp.delete(‘\/users\/:id’, (req, res) => { \/* Delete user *\/ });<\/p>\n<\/div><\/div>

22. How do you implement route parameters in an Express.js application?<\/h3>

Answer:<\/strong><\/p>

Use :parameter<\/strong> in the route path to define route parameters, which can be accessed via req.params<\/strong>.<\/p>

\n

app.get(‘\/users\/:id’, (req, res) => {
\nres.send(`User ID: ${req.params.id}`);
\n});<\/p>\n<\/div><\/div>

23. Write an Express.js route that validates the request body using a middleware function.<\/h3>

Answer:<\/strong><\/p>

Create a middleware function to validate the request body before passing control to the route handler.<\/p>

\n

function validateBody(req, res, next) {
\nif (!req.body.name) return res.status(400).send(‘Name is required’);
\nnext();
\n}<\/p>\n

app.post(‘\/users’, validateBody, (req, res) => {
\nres.send(‘User created’);
\n});<\/p>\n<\/div><\/div>

24. How do you handle CORS in a Node.js application?<\/h3>

Answer:<\/strong><\/p>

Use the cors<\/strong> middleware to enable Cross-Origin Resource Sharing, allowing your API to be accessed from different domains.<\/p>

\n

const cors = require(‘cors’);
\napp.use(cors());<\/p>\n<\/div><\/div>

25. Write a Node.js script that connects to a REST API and logs the response.<\/h3>

Answer:<\/strong><\/p>

Use axios<\/strong> or node-fetch<\/strong> to send a GET request to a REST API and log the response.<\/p>

\n

const axios = require(‘axios’);
\naxios.get(‘https:\/\/jsonplaceholder.typicode.com\/posts’)
\n.then(response => console.log(response.data))
\n.catch(error => console.error(error));<\/p>\n<\/div><\/div>

26. How do you connect a Node.js application to a MongoDB database using Mongoose?<\/h3>

Answer:<\/strong><\/p>

Use Mongoose to define a schema, connect to the MongoDB database, and interact with collections.<\/p>

\n

const mongoose = require(‘mongoose’);
\nmongoose.connect(‘mongodb:\/\/localhost\/mydb’, { useNewUrlParser: true, useUnifiedTopology: true });<\/p>\n<\/div><\/div>

27. Write a Mongoose schema for a User model with fields for name, email, and password.<\/h3>

Answer:<\/strong><\/p>

Define a schema using Mongoose and create a model to interact with the User<\/strong> collection.<\/p>

\n

const userSchema = new mongoose.Schema({
\nname: String,
\nemail: String,
\npassword: String
\n});
\nconst User = mongoose.model(‘User’, userSchema);<\/p>\n<\/div><\/div>

28. How do you perform CRUD operations on a MongoDB collection using Mongoose in Node.js?<\/h3>

Answer:<\/strong><\/p>

Use Mongoose model methods like find<\/strong>, create<\/strong>, update<\/strong>, and delete<\/strong> to perform CRUD operations.<\/p>

\n

User.find({}, (err, users) => { \/* Fetch users *\/ });
\nUser.create({ name: ‘John’ }, (err, user) => { \/* Create user *\/ });
\nUser.updateOne({ _id: id }, { name: ‘Jane’ }, (err) => { \/* Update user *\/ });
\nUser.deleteOne({ _id: id }, (err) => { \/* Delete user *\/ });<\/p>\n<\/div><\/div>

29. How do you handle database errors in a Node.js application using Mongoose?<\/h3>

Answer:<\/strong><\/p>

Use Mongoose’s built-in error handling and validate data before saving it to handle errors gracefully.<\/p>

\n

user.save((err) => {
\nif (err) return console.error(‘Error saving user:’, err);
\nconsole.log(‘User saved successfully’);
\n});<\/p>\n<\/div><\/div>

30. Write a Node.js function that fetches data from a PostgreSQL database using pg module.<\/h3>

Answer:<\/strong><\/p>

Use the pg<\/strong> module to connect to a PostgreSQL database, execute a query, and return the results.<\/p>

\n

const { Client } = require(‘pg’);
\nconst client = new Client();
\nclient.connect();
\nclient.query(‘SELECT * FROM users’, (err, res) => {
\nconsole.log(res.rows);
\nclient.end();
\n});<\/p>\n<\/div><\/div>

31. How do you hash passwords in a Node.js application using bcrypt?<\/h3>

Answer:<\/strong><\/p>

Use bcrypt<\/strong> to hash user passwords before storing them in the database to enhance security.<\/p>

\n

const bcrypt = require(‘bcrypt’);
\nconst saltRounds = 10;
\nbcrypt.hash(‘myPassword’, saltRounds, (err, hash) => {
\n\/\/ Store hash in your password database
\n});<\/p>\n<\/div><\/div>

32. Write a Node.js middleware function to authenticate API requests using JWT.<\/h3>

Answer:<\/strong><\/p>

Use jsonwebtoken<\/strong> to verify the JWT in the request header and authenticate the user.<\/p>

\n

const jwt = require(‘jsonwebtoken’);
\nfunction authenticateToken(req, res, next) {
\nconst token = req.header(‘Authorization’).split(‘ ‘)[1];
\nif (!token) return res.sendStatus(401);
\njwt.verify(token, ‘secretkey’, (err, user) => {
\nif (err) return res.sendStatus(403);
\nreq.user = user;
\nnext();
\n});
\n}<\/p>\n<\/div><\/div>

33. How do you prevent SQL injection attacks in a Node.js application?<\/h3>

Answer:<\/strong><\/p>

Use parameterized queries or ORM libraries like Sequelize to safely execute SQL queries, preventing SQL injection attacks.<\/p>

\n

client.query(‘SELECT * FROM users WHERE id = $1’, [userId], (err, res) => {
\n\/\/ Handle result
\n});<\/p>\n<\/div><\/div>

34. Write a Node.js function to sanitize user input before saving it to the database.<\/h3>

Answer:<\/strong><\/p>

Use libraries like validator<\/strong> to sanitize and validate user input, ensuring data integrity and security.<\/p>

\n

const validator = require(‘validator’);
\nconst sanitizedInput = validator.escape(req.body.input);<\/p>\n<\/div><\/div>

35. How do you implement HTTPS in a Node.js application?<\/h3>

Answer:<\/strong><\/p>

Use the https<\/strong> module to create an HTTPS server with SSL\/TLS certificates, ensuring secure communication.<\/p>

\n

const https = require(‘https’);
\nconst fs = require(‘fs’);
\nconst options = {
\nkey: fs.readFileSync(‘server.key’),
\ncert: fs.readFileSync(‘server.cert’)
\n};
\nhttps.createServer(options, (req, res) => {
\nres.writeHead(200);
\nres.end(‘Secure connection’);
\n}).listen(443);<\/p>\n<\/div><\/div>

36. How do you write a unit test for a Node.js function using Mocha and Chai?<\/h3>

Answer:<\/strong><\/p>

Use Mocha as the testing framework and Chai for assertions to write and run unit tests for Node.js functions.<\/p>

\n

const { expect } = require(‘chai’);
\ndescribe(‘My Function’, () => {
\nit(‘should return true’, () => {
\nconst result = myFunction();
\nexpect(result).to.be.true;
\n});
\n});<\/p>\n<\/div><\/div>

37. Write a Node.js test case that mocks a database call using Sinon.<\/h3>

Answer:<\/strong><\/p>

Use Sinon to create a mock for the database method and test the function without hitting the actual database.<\/p>

\n

const sinon = require(‘sinon’);
\nconst db = require(‘.\/db’);
\nsinon.stub(db, ‘find’).returns([{ id: 1, name: ‘Test’ }]);<\/p>\n<\/div><\/div>

38. How do you handle exceptions and errors in a Node.js application?<\/h3>

Answer:<\/strong><\/p>

Use try…catch<\/strong> blocks to handle synchronous errors and the process.on(‘uncaughtException’)<\/strong> event for global error handling.<\/p>

\n

try {
\nconst data = JSON.parse(invalidJson);
\n} catch (error) {
\nconsole.error(‘JSON parsing error:’, error);
\n}<\/p>\n<\/div><\/div>

39. How do you debug a Node.js application?<\/h3>

Answer:<\/strong><\/p>

Use the built-in Node.js debugger or tools like node-inspect<\/strong> and Chrome DevTools to set breakpoints and inspect variables during execution.<\/p>

\n

node –inspect-brk app.js<\/p>\n<\/div><\/div>

40. Write a Node.js function with proper logging using a logging library like winston.<\/h3>

Answer:<\/strong><\/p>

Use winston<\/strong> to log messages at different levels (info, error) and output them to console or files.<\/p>

\n

const winston = require(‘winston’);
\nconst logger = winston.createLogger({
\ntransports: [new winston.transports.Console()]\n});
\nlogger.info(‘This is an info message’);<\/p>\n<\/div><\/div>

41. How do you deploy a Node.js application to a cloud platform like Heroku?<\/h3>

Answer:<\/strong><\/p>

Create a Procfile<\/strong> and push your code to Heroku using Git to deploy your Node.js application.<\/p>

\n

web: node app.js<\/p>\n<\/div><\/div>

42. How do you manage environment variables in a Node.js application?<\/h3>

Answer:<\/strong><\/p>

Use the dotenv<\/strong> package to load environment variables from a .env<\/strong> file into process.env<\/strong> for use in your application.<\/p>

\n

require(‘dotenv’).config();
\nconst port = process.env.PORT || 3000;<\/p>\n<\/div><\/div>

43. How do you implement clustering in Node.js to improve performance?<\/h3>

Answer:<\/strong><\/p>

Use the cluster<\/strong> module to create multiple worker processes that share the same port, improving performance on multi-core systems.<\/p>

\n

const cluster = require(‘cluster’);
\nif (cluster.isMaster) {
\nfor (let i = 0; i < 4; i++) cluster.fork();
\n} else {
\nrequire(‘.\/app’);
\n}<\/p>\n<\/div><\/div>

44. Write a Node.js script to measure the execution time of a function.<\/h3>

Answer:<\/strong><\/p>

Use console.time<\/strong> and console.timeEnd<\/strong> to measure and log the execution time of a function.<\/p>

\n

console.time(‘executionTime’);
\nmyFunction();
\nconsole.timeEnd(‘executionTime’);<\/p>\n<\/div><\/div>

45. How do you optimize a Node.js application for high concurrency?<\/h3>

Answer:<\/strong><\/p>

Optimize for high concurrency by using non-blocking I\/O operations, clustering, and efficiently managing memory and resources.<\/p>

46. How do you implement WebSockets in a Node.js application for real-time communication?<\/h3>

Answer:<\/strong><\/p>

Use the ws<\/strong> library to create a WebSocket server that handles real-time bidirectional communication with clients.<\/p>

\n

const WebSocket = require(‘ws’);
\nconst wss = new WebSocket.Server({ port: 8080 });<\/p>\n

wss.on(‘connection’, ws => {
\nws.on(‘message’, message => console.log(`Received: ${message}`));
\nws.send(‘Hello, client!’);
\n});<\/p>\n<\/div><\/div>

47. Write a Node.js function that uses child_process to execute a shell command and capture the output.<\/h3>

Answer:<\/strong><\/p>

Use the exec<\/strong> function from the child_process<\/strong> module to run a shell command and handle the output asynchronously.<\/p>

\n

const { exec } = require(‘child_process’);
\nexec(‘ls’, (error, stdout, stderr) => {
\nif (error) console.error(`Error: ${error.message}`);
\nconsole.log(`Output: ${stdout}`);
\n});<\/p>\n<\/div><\/div>

48. How do you implement a rate limiter in an Express.js application to prevent abuse?<\/h3>

Answer:<\/strong><\/p>

Use the express-rate-limit<\/strong> middleware to limit the number of requests from a single IP address.<\/p>

\n

const rateLimit = require(‘express-rate-limit’);
\nconst limiter = rateLimit({ windowMs: 15 * 60 * 1000, max: 100 });
\napp.use(limiter);<\/p>\n<\/div><\/div>

49. How do you create a RESTful API that supports pagination in Node.js?<\/h3>

Answer:<\/strong><\/p>

Use query parameters to handle pagination and return a subset of results based on limit<\/strong> and offset<\/strong>.<\/p>

\n

app.get(‘\/users’, (req, res) => {
\nconst limit = parseInt(req.query.limit, 10) || 10;
\nconst offset = parseInt(req.query.offset, 10) || 0;
\nUser.find().skip(offset).limit(limit).exec((err, users) => {
\nres.json(users);
\n});
\n});<\/p>\n<\/div><\/div>

50. How do you implement a custom event emitter in Node.js?<\/h3>

Answer:<\/strong><\/p>

Extend the EventEmitter<\/strong> class to create a custom event emitter and emit custom events.<\/p>

\n

const EventEmitter = require(‘events’);
\nclass MyEmitter extends EventEmitter {}
\nconst myEmitter = new MyEmitter();
\nmyEmitter.on(‘event’, () => console.log(‘Event triggered’));
\nmyEmitter.emit(‘event’);<\/p>\n<\/div><\/div>

Final Words<\/h2>

Getting ready for an interview can feel overwhelming, but going through these Node.js fresher interview questions can help you feel more confident.<\/p>

With the right preparation, you’ll ace your Node.js interview but don’t forget to practice the Node.js basic coding and API-related interview questions too.<\/p>

Frequently Asked Questions<\/h2>

1. What are the most common interview questions for Node JS?<\/h3>

The most common interview questions for Node.js often cover topics like asynchronous programming, event-driven architecture, Express.js, middleware, and RESTful API development.<\/p>

2. What are the important Node JS topics freshers should focus on for interviews?<\/h3>

The important Node.js topics freshers should focus on include the event loop, callbacks, promises, modules, and handling asynchronous operations.<\/p>

3. How should freshers prepare for Node JS technical interviews?<\/h3>

Freshers should prepare for Node.js technical interviews by building small projects, practicing common coding patterns, and understanding core concepts like middleware and API routing.<\/p>

4. What strategies can freshers use to solve Node JS coding questions during interviews?<\/h3>

Strategies freshers can use include breaking down the problem, leveraging Node.js built-in modules, and writing clean, modular code.<\/p>

5. Should freshers prepare for advanced Node JS topics in interviews?<\/h3>

Yes, freshers should prepare for advanced Node.js topics like microservices, real-time communication with WebSockets, and working with databases, depending on the job role.<\/p>

Explore More Node JS Resources<\/h2>