Top 100 Node.js Interview Questions and Answers for Hindi speakers

Node.js एक open-source, cross-platform, JavaScript runtime environment है जो वेब डेवलपमेंट के लिए उपयोग किया जाता है। इसे विशेष रूप से server-side scripting के लिए डिज़ाइन किया गया है। इसकी मुख्य विशेषताएं आसान एवं बहुत तेज एप्लीकेशन्स डेवलप करने के लिए हैं। यह अलग-अलग प्लेटफार्मों पर चलने वाली JavaScript कोड को संचालित करने में मदद करता है।

नीचे दिए गए हैं Node.js के Top 100 Interview Questions and Answers-

1. What is Node.js?
   Node.js is a server-side platform built on Google Chrome’s V8 JavaScript engine. It is used to build fast and scalable network applications, as it is capable of handling a large number of connections simultaneously.

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

   • Asynchronous and Event Driven
   • Very Fast
   • Single Threaded but Highly Scalable

3. What is npm?
   npm stands for Node Package Manager. It is the default package manager for Node.js, and it allows developers to install and manage external Node.js modules easily.

4. How can you install a package using npm?
   To install a package using npm, you can run the following command in your terminal:
   npm install

5. What is the difference between Node.js and Ajax?
   Node.js is a server-side platform, whereas Ajax is a client-side technology used for making asynchronous requests to the server.

6. Explain the concept of event-driven programming in Node.js.
   In Node.js, all I/O operations are performed asynchronously, which means that the code continues to run even if the I/O operation is still in progress. When the I/O operation is completed, a callback function is called to handle the result. This is known as event-driven programming.

7. What is the purpose of the callback function in Node.js?
   The callback function in Node.js is used to handle the result of asynchronous operations. It is passed as an argument to asynchronous functions and is called once the operation is completed.

8. How can you create a simple HTTP server in Node.js?
   To create a simple HTTP server in Node.js, you can use the following code:
   const http = require(‘http’);

const server = http.createServer((req, res) => {
res.end(‘Hello World!’);
});

server.listen(3000, () => {
console.log(‘Server is running on port 3000’);
});

1. How can you read data from a file using Node.js?
   To read data from a file using Node.js, you can use the fs module. Here is an example code snippet:
   const fs = require(‘fs’);

fs.readFile(‘file.txt’, ‘utf8’, (err, data) => {
if (err) {
console.error(err);
return;
}

console.log(data);

});

1. What is the purpose of the util module in Node.js?
   The util module in Node.js provides utility functions that are helpful when working with objects and functions. It includes functions for debugging, formatting, and managing objects.

2. How can you use the cluster module in Node.js to improve performance?
   The cluster module in Node.js allows you to create multiple worker processes that can share the same server port. This can help improve performance by utilizing all available CPU cores.

3. What is the purpose of the EventEmitter class in Node.js?
   The EventEmitter class in Node.js is used to create custom events and handle event-driven programming. It provides methods for emitting events, adding event listeners, and removing event listeners.

4. How can you handle errors in Node.js?
   You can handle errors in Node.js by using try-catch blocks or by using the ‘error’ event. In the case of asynchronous operations, you can pass the error as the first argument to the callback function.

5. What is the difference between the ‘require’ and ‘import’ statements in Node.js?
   The ‘require’ statement is used to import modules in Node.js, while the ‘import’ statement is used in ES6 to import modules in JavaScript. ‘import’ statements are not natively supported in Node.js, but you can use them with the help of a transpiler like Babel.

6. How can you debug a Node.js application?
   You can debug a Node.js application using the built-in debugger or by using third-party tools like Visual Studio Code, WebStorm, or Chrome DevTools. You can set breakpoints, inspect variables, and step through the code to identify and fix issues.

7. What is the purpose of the http module in Node.js?
   The http module in Node.js provides functionality for creating HTTP servers and making HTTP requests. It allows you to handle incoming HTTP requests, send HTTP responses, and set up routes for different endpoints.

8. How can you handle POST requests in Node.js?
   To handle POST requests in Node.js, you can use the ‘body-parser’ middleware to parse the request body. You can then access the data sent in the request body using the ‘req.body’ object.

9. What is the purpose of the path module in Node.js?
   The path module in Node.js provides utilities for working with file paths. It allows you to join, resolve, and normalize file paths, as well as extract information about the path such as the directory name, file name, and file extension.

10. How can you create a RESTful API in Node.js?
    To create a RESTful API in Node.js, you can use the express framework. You can define routes for different HTTP methods (GET, POST, PUT, DELETE) and handle requests to these routes by writing corresponding callback functions.

11. What is the ‘global’ object in Node.js?
    The ‘global’ object in Node.js is a global object that represents the global scope. It provides properties and methods that are global to all modules in a Node.js application.

12. How can you handle file uploads in Node.js?
    To handle file uploads in Node.js, you can use the ‘multer’ middleware. Multer allows you to parse multipart/form-data and save the uploaded files to a specified location on the server.

13. What is the purpose of the buffer class in Node.js?
    The buffer class in Node.js is used to represent binary data. It allows you to work with raw data in memory, such as reading from files, sockets, or other sources, and converting it to string or other formats.

14. How can you spawn a child process in Node.js?
    You can spawn a child process in Node.js using the ‘child_process’ module. The ‘spawn’ method allows you to execute a command in a new process, while the ‘fork’ method allows you to fork a new Node.js process.

15. What is the purpose of the url module in Node.js?
    The url module in Node.js provides utilities for parsing and formatting URLs. It allows you to parse a URL string into its constituent parts, such as the protocol, hostname, path, and query parameters.

16. How can you create a WebSocket server in Node.js?
    To create a WebSocket server in Node.js, you can use the ‘ws’ module. You can create a server instance, set up event listeners for connection and message events, and broadcast messages to all clients connected to the server.

17. What is the purpose of the querystring module in Node.js?
    The querystring module in Node.js provides utilities for parsing and formatting query strings. It allows you to convert query parameters to and from objects, as well as stringify and parse query strings.

18. How can you write unit tests for a Node.js application?
    You can write unit tests for a Node.js application using a testing framework like Mocha, Jest, or Chai. You can define test cases, assert expected outcomes, and run the tests using the testing framework’s command line interface.

19. What is the purpose of the crypto module in Node.js?
    The crypto module in Node.js provides cryptographic functionality for creating secure hashes, encrypting and decrypting data, and generating secure random numbers. It allows you to perform secure operations using algorithms like AES, RSA, and SHA-256.

20. How can you use middleware in Node.js?
    Middleware in Node.js is a function that is executed before or after the main request handler. You can use middleware to perform common tasks like logging, authentication, error handling, and parsing request data. Middleware functions can be chained together in a sequence using the ‘use’ method.

21. What is the purpose of the url.parse() method in Node.js?
    The url.parse() method in Node.js is used to parse a URL string into its constituent parts. It returns an object with properties like protocol, hostname, port, path, query, and hash.

22. How can you use the cluster module in Node.js to create a multi-process server?
    To create a multi-process server using the cluster module in Node.js, you can use the following code:
    const cluster = require(‘cluster’);
    const http = require(‘http’);
    const numCPUs = require(‘os’).cpus().length;

if (cluster.isMaster) {
console.log(Master ${process.pid} is running);

for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
}

cluster.on('exit', (worker, code, signal) => {
    console.log(`Worker ${worker.process.pid} died`);
});

} else {
http.createServer((req, res) => {
res.writeHead(200);
res.end(‘Hello World’);
}).listen(8000);

console.log(`Worker ${process.pid} started`);

}

1. How can you optimize the performance of a Node.js application?
   To optimize the performance of a Node.js application, you can:

   • Use asynchronous I/O operations
   • Cache data in memory
   • Use a load balancer to distribute incoming requests
   • Minimize the use of synchronous code
   • Profile and monitor the application using tools like New Relic or PM2

2. What is the purpose of the timing functions in Node.js?
   The timing functions in Node.js, such as setTimeout and setInterval, are used to schedule tasks to run at a specific time or at intervals. They allow you to execute code asynchronously and delay execution to prevent blocking the event loop.

3. How can you use the fs module in Node.js to read a directory?
   To read a directory using the fs module in Node.js, you can use the fs.readdir() method. Here is an example code snippet:
   const fs = require(‘fs’);

fs.readdir(‘/path/to/directory’, (err, files) => {
if (err) {
console.error(err);
return;
}

files.forEach(file => {
    console.log(file);
});

});

1. What is the purpose of the zlib module in Node.js?
   The zlib module in Node.js provides functionality for compression and decompression of data using algorithms like Gzip and Deflate. It allows you to reduce the size of data for more efficient transmission over the network.

2. How can you use the readline module in Node.js to read user input?
   To read user input using the readline module in Node.js, you can create a readline interface and listen for the ‘line’ event. Here is an example code snippet:
   const readline = require(‘readline’);

const rl = readline.createInterface({
input: process.stdin,
output: process.stdout
});

rl.question(‘What is your name? ‘, (answer) => {
console.log(Hello, ${answer}!);
rl.close();
});

1. What is the purpose of the EventEmitter class in Node.js?
   The EventEmitter class in Node.js allows you to create custom events and handle event-driven programming. It provides methods for emitting events, adding event listeners, and removing event listeners.

2. How can you use the fs module in Node.js to write data to a file?
   To write data to a file using the fs module in Node.js, you can use the fs.writeFile() method. Here is an example code snippet:
   const fs = require(‘fs’);

fs.writeFile(‘file.txt’, ‘Hello World!’, (err) => {
if (err) {
console.error(err);
return;
}

console.log('Data written to file');

});

1. What is the purpose of the os module in Node.js?
   The os module in Node.js provides utilities for working with the operating system. It allows you to access information like CPU architecture, memory usage, network interfaces, and operating system platform.

2. How can you use the net module in Node.js to create a TCP server?
   To create a TCP server using the net module in Node.js, you can use the net.createServer() method. Here is an example code snippet:
   const net = require(‘net’);

const server = net.createServer((socket) => {
socket.write(‘Hello World’);
socket.end();
});

server.listen(8000, () => {
console.log(‘Server is running on port 8000’);
});

1. How can you use the path module in Node.js to join file paths?
   To join file paths using the path module in Node.js, you can use the path.join() method. Here is an example code snippet:
   const path = require(‘path’);

const filePath = path.join(__dirname, ‘file.txt’);
console.log(filePath);

1. What is the purpose of the dns module in Node.js?
   The dns module in Node.js provides utilities for working with the Domain Name System. It allows you to perform DNS queries, resolve domain names to IP addresses, and perform reverse DNS lookups.

2. How can you use the util module in Node.js to format strings?
   To format strings using the util module in Node.js, you can use the util.format() method. Here is an example code snippet:
   const util = require(‘util’);

const formattedString = util.format(‘Hello, %s!’, ‘World’);
console.log(formattedString);

1. How can you use the vm module in Node.js to run JavaScript code in a sandbox?
   To run JavaScript code in a sandbox using the vm module in Node.js, you can create a new context and use the vm.runInContext() method. Here is an example code snippet:
   const vm = require(‘vm’);

const sandbox = {
message: ‘Hello World’
};

vm.createContext(sandbox);
vm.runInContext(‘console.log(message)’, sandbox);

1. What is the purpose of the async module in Node.js?
   The async module in Node.js provides utilities for working with asynchronous JavaScript. It includes functions like async.parallel, async.series, and async.waterfall, which help you manage asynchronous tasks in a more organized way.

2. How can you use the crypto module in Node.js to generate a secure hash?
   To generate a secure hash using the crypto module in Node.js, you can use the crypto.createHash() method. Here is an example code snippet:
   const crypto = require(‘crypto’);

const hash = crypto.createHash(‘sha256’);
hash.update(‘Hello World’);
const hashedValue = hash.digest(‘hex’);

console.log(hashedValue);

1. How can you use the http module in Node.js to make an HTTP request?
   To make an HTTP request using the http module in Node.js, you can use the http.request() method. Here is an example code snippet:
   const http = require(‘http’);

http.get(‘http://www.example.com‘, (res) => {
let data = ”;

res.on('data', (chunk) => {
    data += chunk;
});

res.on('end', () => {
    console.log(data);
});

});

1. What is the purpose of the cluster module in Node.js?
   The cluster module in Node.js allows you to create multiple worker processes that can share the same server port. This can help improve performance by utilizing all available CPU cores and handling a larger number of concurrent requests.

2. What is the purpose of the readline module in Node.js?
   The readline module in Node.js provides an interface for reading input from a readable stream, such as the process.stdin stream. It allows you to read user input from the command line and create interactive command line interfaces.

3. How can you use the cluster module in Node.js to create a multi-threaded server?
   To create a multi-threaded server using the cluster module in Node.js, you can use the cluster.fork() method to spawn multiple worker processes. Each worker process runs on a separate thread and shares the same server port.

4. How can you use the express framework to create a simple web server in Node.js?
   To create a simple web server using the express framework in Node.js, you can use the following code:
   const express = require(‘express’);
   const app = express();

app.get(‘/’, (req, res) => {
res.send(‘Hello World’);
});

app.listen(3000, () => {
console.log(‘Server is running on port 3000’);
});

1. How can you use the request module in Node.js to make an HTTP request?
   To make an HTTP request using the request module in Node.js, you can install the request module using npm and use the request() function. Here is an example code snippet:
   const request = require(‘request’);

request(‘http://www.example.com‘, (error, response, body) => {
console.log(body);
});

1. What is the purpose of the debug module in Node.js?
   The debug module in Node.js provides utilities for debugging applications. It allows you to log debug messages and set debug levels depending on the environment.

2. How can you use the npm module in Node.js to install a package?
   To install a package using the npm module in Node.js, you can use the npm install command followed by the package name. Here is an example command:
   npm install express

3. What is the purpose of the querystring module in Node.js?
   The querystring module in Node.js provides utilities for parsing and formatting query strings. It allows you to convert query parameters to and from objects, as well as stringify and parse query strings.

4. How can you use the fs module in Node.js to create a new file?
   To create a new file using the fs module in Node.js, you can use the fs.writeFile() method. Here is an example code snippet:
   const fs = require(‘fs’);

fs.writeFile(‘file.txt’, ‘Hello World’, (err) => {
if (err) {
console.error(err);
return;
}

console.log('File created');

});

1. What is the purpose of the assert module in Node.js?
   The assert module in Node.js provides utilities for writing tests in assertion style. It allows you to assert expected outcomes and throw an error if the assertion fails.

2. How can you use the path module in Node.js to get the file extension?
   To get the file extension using the path module in Node.js, you can use the path.extname() method. Here is an example code snippet:
   const path = require(‘path’);

const fileExtension = path.extname(‘file.txt’);
console.log(fileExtension);

1. How can you use the util module in Node.js to inherit from