Top Basic Node.js Interview Questions and Answers for Capgemini

Introduction

Are you preparing for a Node.js interview at Capgemini? Node.js is an open-source, cross-platform JavaScript runtime environment widely used for building fast, scalable, and real-time backend applications. Capgemini frequently evaluates candidates on asynchronous programming, event-driven architecture, API development, Express.js, and performance optimization in Node.js.

This blog provides a comprehensive list of basic Node.js interview questions to help freshers and experienced developers succeed in their Capgemini technical interview.

✔ Covers essential Node.js concepts
✔ SEO-optimized for better ranking
✔ Includes practical examples
✔ Suitable for freshers and experienced developers

📌 Bookmark this page and revise these questions before your Capgemini Node.js interview! 🚀

Top Basic Node.js Interview Questions and Answers

1. What is Node.js?

Answer: Node.js is an open-source, event-driven, non-blocking JavaScript runtime environment that runs on Chrome’s V8 engine. It is used to build scalable and high-performance backend applications.

2. What are the key features of Node.js?

Answer:

• Asynchronous and Event-driven – Uses a non-blocking I/O model
• Single-threaded but highly scalable – Handles multiple requests efficiently
• Built-in Package Manager (NPM) – Manages reusable modules
• Cross-platform – Works on Windows, macOS, and Linux
• Fast Execution – Runs on Google’s V8 engine

3. What is the difference between JavaScript and Node.js?

Answer:

4. What is an event-driven architecture in Node.js?

Answer: Node.js uses an event-driven architecture, where the EventEmitter module listens for and handles events asynchronously.

Example:

const EventEmitter = require("events");
const event = new EventEmitter();

event.on("message", () => {
  console.log("Event triggered!");
});

event.emit("message"); // Output: Event triggered!

5. What is the difference between synchronous and asynchronous programming in Node.js?

Answer:

6. What is the purpose of NPM (Node Package Manager)?

Answer: NPM is used to install, update, and manage Node.js packages and dependencies.

Example to install a package:

npm install express

7. What are Node.js modules?

Answer: Modules in Node.js are reusable blocks of code that can be exported and imported.

Example:

// myModule.js
module.exports = function () {
  console.log("Hello from Module!");
};

// app.js
const myModule = require("./myModule");
myModule();

8. What is the difference between CommonJS and ES6 modules?

Answer:

9. What is an HTTP module in Node.js?

Answer: The http module is used to create an HTTP server.

Example:

const http = require("http");

const server = http.createServer((req, res) => {
  res.write("Hello, Capgemini!");
  res.end();
});

server.listen(3000, () => console.log("Server running on port 3000"));

10. What is Express.js in Node.js?

Answer: Express.js is a lightweight and fast web framework for Node.js used to build RESTful APIs.

Example of an Express server:

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

app.get("/", (req, res) => {
  res.send("Welcome to Capgemini!");
});

app.listen(3000, () => console.log("Server started on port 3000"));

11. What are middleware functions in Express.js?

Answer: Middleware functions handle requests and responses before they reach the final route handler.

Example:

app.use((req, res, next) => {
  console.log("Middleware executed!");
  next();
});

12. What is the difference between GET and POST methods in Node.js?

Answer:

Example GET request:

app.get("/users", (req, res) => {
  res.send("List of users");
});

Example POST request:

app.post("/users", (req, res) => {
  res.send("User created");
});

13. How do you handle errors in Node.js?

Answer: Using try-catch for synchronous code and .catch() for promises.

Example:

try {
  throw new Error("Something went wrong!");
} catch (error) {
  console.log(error.message);
}

For promises:

fetchData().catch((err) => console.log(err));

14. What is a callback function in Node.js?

Answer: A callback function executes after an asynchronous operation is complete.

Example:

fs.readFile("file.txt", "utf8", (err, data) => {
  if (err) throw err;
  console.log(data);
});

15. What is the purpose of process.nextTick()?

Answer: process.nextTick() executes a function immediately after the current execution completes.

Example:

process.nextTick(() => {
  console.log("Executed in next tick");
});

16. What is clustering in Node.js?

Answer: Clustering allows running multiple Node.js instances to handle more requests.

Example:

const cluster = require("cluster");

if (cluster.isMaster) {
  cluster.fork();
} else {
  console.log("Worker process running");
}

17. What is CORS in Node.js?

Answer: CORS (Cross-Origin Resource Sharing) allows API requests from different origins.

Example using Express:

const cors = require("cors");
app.use(cors());

18. What is the difference between PUT and PATCH in REST APIs?

Answer:

19. What is JWT authentication in Node.js?

Answer: JSON Web Token (JWT) is used for secure API authentication.

Example using jsonwebtoken:

const jwt = require("jsonwebtoken");

const token = jwt.sign({ user: "capgemini" }, "secretKey");
console.log(token);

20. What is the difference between localStorage, sessionStorage, and cookies?

Answer: