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NodeJS Interview Questions and Answers

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Ques 26. Explain the purpose of the 'dotenv' module in Node.js.

The 'dotenv' module is used to load environment variables from a '.env' file into 'process.env'. It is commonly used in Node.js applications to manage configuration variables.

Example:

require('dotenv').config();

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Ques 27. What is the role of the 'WebSocket' protocol in Node.js?

WebSocket is a communication protocol that provides full-duplex communication channels over a single, long-lived connection. In Node.js, the 'ws' library is commonly used to implement WebSocket servers and clients.

Example:

const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

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Ques 28. Explain the concept of 'middleware chaining' in Express.js.

Middleware chaining in Express.js is the process of sequentially applying multiple middleware functions to a request. Each middleware function can modify the request and response objects or terminate the request-response cycle.

Example:

app.use(middleware1);
app.use(middleware2);
app.use(middleware3);

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Ques 29. What is the purpose of the 'pm2' module in Node.js?

'pm2' is a process manager for Node.js applications. It allows you to run, monitor, and manage Node.js processes, enabling features like automatic restarts, clustering, and log management.

Example:

pm2 start app.js

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Ques 30. Explain the purpose of the 'CORS' middleware in Express.js.

CORS (Cross-Origin Resource Sharing) middleware in Express.js is used to enable or restrict cross-origin HTTP requests. It adds the necessary headers to allow or deny requests from different origins.

Example:

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

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