✅ Most Common Web Development Interview Q&A 💡👨‍💻

🖥️ Frontend (HTML, CSS, JavaScript)

1️⃣ Q: What’s the difference between relative, absolute, fixed & sticky positioning in CSS?
👉 Relative: Moves relative to its normal position.
👉 Absolute: Positioned relative to nearest positioned ancestor.
👉 Fixed: Stays fixed relative to the viewport.
👉 Sticky: Switches between relative and fixed when scrolling.

2️⃣ Q: Explain the CSS Box Model.
👉 It consists of: Content → Padding → Border → Margin

3️⃣ Q: How do you improve website performance?
👉 Minify files, use lazy-loading, enable caching, code splitting, use CDN.

4️⃣ Q: What’s the difference between == and === in JS?
👉 == compares ×value only× (type coercion), === compares ×value + type×.

5️⃣ Q: How does event delegation work?
👉 Attach a single event listener to a parent element to handle events from its children.

6️⃣ Q: What are Promises & how is async/await different?
👉 Promises handle async operations. async/await is syntactic sugar for cleaner code.

7️⃣ Q: How does the browser render a page (Critical Rendering Path)?
👉 HTML → DOM + CSSOM → Render Tree → Layout → Paint

🛠️ Backend (Node.js, Express, APIs)

8️⃣ Q: What is middleware in Express?
👉 Functions that execute during request → response cycle. Used for auth, logging, etc.

9️⃣ Q: REST vs GraphQL?
👉 REST: Multiple endpoints. GraphQL: Single endpoint, fetch what you need.

🔟 Q: How do you handle authentication in Node.js?
👉 JWT tokens, sessions, OAuth strategies (like Google login).

1️⃣1️⃣ Q: Common HTTP status codes?
👉 200 = OK, 201 = Created, 400 = Bad Request, 401 = Unauthorized, 404 = Not Found, 500 = Server Error

1️⃣2️⃣ Q: What is CORS and how to enable it?
👉 Cross-Origin Resource Sharing — restricts requests from different domains.
Enable in Express with cors package:

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

🗂️ Database & Full Stack

1️⃣3️⃣ Q: SQL vs NoSQL – When to choose what?
👉 SQL: Structured, relational data (MySQL, Postgres)
👉 NoSQL: Flexible, scalable, unstructured (MongoDB)

1️⃣4️⃣ Q: What is Mongoose in MongoDB apps?
👉 ODM (Object Data Modeling) library for MongoDB. Defines schemas, handles validation & queries.

🌐 General / Deployment

1️⃣5️⃣ Q: How to deploy a full-stack app?
👉 Frontend: Vercel / Netlify
👉 Backend: Render / Heroku / Railway
👉 Add environment variables & connect frontend to backend via API URL.

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