Node JS Interview Questions (Basic to Advanced) Part 4

Today I am continuing Node JS Interview Question Series. This series will be based on 5 parts covering the important questions asked in interviews from Basic to Advanced

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1. How do you use promises in Node.js?

Promises are a way to handle asynchronous operations in a more structured and organized way. Here's an example:

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function fetchData() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      const data = 'Data fetched';
      resolve(data);
    }, 2000);
  });
}

fetchData().then((data) => {
  console.log(data);
}).catch((error) => {
  console.error(error);
});

2. What are async/await in Node.js?

Async/await is a newer syntax introduced in Node.js 8 for handling asynchronous operations. It allows you to write asynchronous code that looks more like synchronous code. Here's an example:

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async function fetchData() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      const data = 'Data fetched';
      resolve(data);
    }, 2000);
  });
}

async function main() {
  const data = await fetchData();
  console.log(data);
}

main().catch((error) => {
  console.error(error);
});

3. How do you use middleware in Node.js?

Middleware is a function that sits between a request and a response in a Node.js application. It can be used to modify requests and responses, or to perform additional processing. Here's an example:

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function logger(req, res, next) {
  console.log(`${req.method} ${req.url}`);
  next();
}

app.use(logger);

4. How do you use Express.js in Node.js?

Express.js is a popular Node.js web framework used for building server-side applications. Here's an example of creating a simple Express.js server:

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const express = require('express');

const app = express();

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

app.listen(3000, () => {
  console.log('Server running on <http://localhost:3000/>');
});

5. How do you use Socket.io in Node.js?

Socket.io is a library that allows real-time, bi-directional communication between clients and servers in a Node.js application. Here's an example of creating a simple Socket.io server:

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const http = require('http');
const io = require('socket.io');

const server = http.createServer((req, res) => {
  res.writeHead(200);
  res.end('Hello, World!');
});

const socket = io(server);

socket.on('connection', (client) => {
  console.log('Client connected');
});

server.listen(3000, () => {
  console.log('Server running on <http://localhost:3000/>');
});

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