Node.js

Question 1

What is Node.js and how does it work?

Answer 1

Node.js is a runtime that lets you run JavaScript on the server. It works using an event loop to handle tasks asynchronously.

Question 2

What is the difference between CommonJS and ES Modules?

Answer 2

CommonJS uses require() and module.exports, while ES Modules use import and export, following modern JavaScript standards.

Question 3

How do you initialize a Node.js project?

Answer 3

Run ‘npm init’ in your terminal to create a package.json file for your project.

Question 4

What is npm and how is it used?

Answer 4

npm is a package manager for Node.js. Use it to install packages with ‘npm install package-name’.

Question 5

What is Express.js and why is it commonly used with Node.js?

Answer 5

Express.js is a framework that makes it easy to build web apps and APIs with Node.js due to its simplicity and flexibility.

Question 6

What is middleware in Express?

Answer 6

Middleware are functions that run during the request-response cycle, like logging or authentication.

Question 7

How do you handle routing in Express?

Answer 7

Use app.get(), app.post(), etc., with a path and callback, e.g., app.get(‘/home’, (req, res) => res.send(‘Home’)).

Question 8

What is the difference between req.params

Answer 8

req.query

Question 9

How do you send a JSON response from an Express route?

Answer 9

Use res.json({ key: value }), e.g., res.json({ message: ‘Success’ }).

Question 10

How do you handle errors in Express?

Answer 10

Use a middleware with (err, req, res, next) => res.status(500).send(err) to catch and respond to errors.

Question 11

What is the Event Loop in Node.js?

Answer 11

The event loop manages asynchronous tasks, allowing Node.js to handle many operations without blocking.

Question 12

What are Streams in Node.js and when should you use them?

Answer 12

Streams handle data in chunks, useful for large files or real-time data like video streaming.

Question 13

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

Answer 13

Synchronous code runs one at a time, blocking others, while asynchronous code runs in the background, like file reads.

Question 14

How do Promises and async/await work in Node.js?

Answer 14

Promises handle async tasks with .then/.catch, and async/await makes it look like sync code with try/catch.

Question 15

How do you connect a Node.js app to a MongoDB database using Mongoose?

Answer 15

Use mongoose.connect(‘mongodb://localhost/dbname’) and define schemas to interact with the database.

Question 16

What are environment variables and how are they managed in a Node.js app?

Answer 16

Environment variables store config data (e.g., API keys). Manage them with a .env file and the dotenv package.

Question 17

How do you implement user authentication in Express?

Answer 17

Use middleware like passport.js with strategies (e.g., local or JWT) to verify user logins.

Question 18

What is CORS and how do you handle it in Express?

Answer 18

CORS is a security feature blocking cross-origin requests. Handle it with the cors middleware.

Question 19

How do you structure a scalable Node.js project?

Answer 19

Organize into folders like routes, controllers, and models, keeping code modular and reusable.

Question 20

How do you handle file uploads in Node.js?

Answer 20

Use the multer middleware to process and save uploaded files from forms.

Question 21

How does Node.js handle concurrency with a single-threaded architecture?

Answer 21

It uses the event loop and libuv to handle many connections concurrently without multiple threads.

Question 22

What is clustering in Node.js and when should you use it?

Answer 22

Clustering uses multiple processes to use all CPU cores, useful for high-traffic apps.

Question 23

How do you handle rate limiting and brute-force protection in Express apps?

Answer 23

Use packages like express-rate-limit to limit requests and prevent brute-force attacks.

Question 24

What are WebSockets and how are they implemented in Node.js?

Answer 24

WebSockets provide real-time two-way communication. Implement with the ws library or Socket.io.

Question 25

How do you create RESTful APIs using Express?

Answer 25

Design APIs with standard HTTP methods (GET, POST, etc.) and clear endpoints, e.g., /api/users.

Question 26

How do you create and verify JWT tokens for authentication?

Answer 26

Create with jsonwebtoken.sign(), verify with jsonwebtoken.verify() using a secret key.

Question 27

What is the difference between MVC and layered architecture in backend apps?

Answer 27

MVC separates Model, View, Controller; layered architecture splits into data, business, and presentation layers.

Question 28

How do you implement input validation and sanitization in Express?

Answer 28

Use express-validator to check and clean input data before processing.

Question 29

How do you handle logging and monitoring in a Node.js production environment?

Answer 29

Use Winston or Bunyan for logging, and tools like New Relic for monitoring performance.

Question 30

What are some best practices for securing a Node.js application?

Answer 30

Use HTTPS, sanitize inputs, limit headers with Helmet, and keep dependencies updated.