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🚀 Web Development Interview Questions with Answers — Part 5: Node.js 🧠 111. What is Node.js? Node.js is a JavaScript runtime built on Chrome’s V8 engine. It allows JavaScript to run outside the browser. Features: ✅ Fast execution ✅ Event-driven ✅ Non-blocking I/O ✅ Scalable applications Example: console.log("Hello Node.js"); 🧠 112. Why Use Node.js? Advantages: ✅ Fast performance ✅ Single programming language for frontend & backend ✅ Handles multiple requests efficiently ✅ Huge npm ecosystem Best Use Cases: • APIs • Real-time apps • Chat applications • Streaming services 🧠 113. What is npm? npm stands for: 👉 Node Package Manager Used to install libraries/packages. Example: npm install express Uses: • Install packages • Manage dependencies • Run scripts 🧠 114. Difference Between CommonJS and ES Modules CommonJS : Uses require() : Uses module.exports ES Modules : Uses import : Uses export CommonJS: const fs = require("fs"); ES Modules: import fs from "fs"; 🧠 115. What is Express.js? Express.js is a minimal backend framework for Node.js. Features: ✅ Routing ✅ Middleware support ✅ API development Example: const express = require("express"); const app = express(); app.get("/", (req, res) => { res.send("Hello"); }); 🧠 116. What is Middleware? Middleware functions execute between: Request → Response Uses: • Authentication • Logging • Validation Example: app.use((req, res, next) => { console.log("Middleware"); next(); }); 🧠 117. What is REST API? REST API follows REST architecture principles. Common Methods: • GET • POST • PUT • DELETE Example: app.get("/users", (req, res) => { res.json(users); }); 🧠 118. Difference Between PUT and PATCH PUT : Updates entire resource PATCH : Updates partial resource Example: PUT /user/1 PATCH /user/1 🧠 119. What is JWT? JWT stands for: 👉 JSON Web Token Used for authentication. Structure: Header.Payload.Signature Benefits: ✅ Secure authentication ✅ Stateless sessions 🧠 120. What is Authentication vs Authorization? Authentication : Verifies identity Authorization : Verifies permissions Example: • Login → Authentication • Admin access → Authorization 🧠 121. What is CORS? CORS stands for: 👉 Cross-Origin Resource Sharing It controls resource sharing between different domains. Example: app.use(cors()); 🧠 122. What is dotenv? dotenv loads environment variables from .env file. Example: require("dotenv").config(); .env PORT=5000 🧠 123. What is Event Loop? Event loop handles asynchronous operations in Node.js. Process: 1. Executes synchronous code 2. Handles callbacks 3. Processes async tasks Benefits: ✅ Non-blocking execution ✅ Efficient concurrency 🧠 124. What is Non-Blocking I/O? Node.js can process multiple requests without waiting. Benefits: ✅ Faster performance ✅ Better scalability 🧠 125. What is package.json? package.json stores project metadata and dependencies.