Next.js useEffect Hook: Side Effects & Cleanup

🚨 React Interview Question That Confuses 90% Developers Let’s test your React fundamentals 👇 import { useState } from "react"; export default function App() { const [count, setCount] = useState(0); function handleClick() { setCount(count + 1); setCount(count + 2); setCount(count + 3); console.log(count); } return ( <> <h1>{count}</h1> <button onClick={handleClick}>Click</button> </> ); } 👉 What will be the output? 1️⃣ Console output? 2️⃣ Final UI value? ⚡ Bonus: Why doesn’t it become 3 (or even 6)? 👇 Think before reading the answer 👇 — — — — — — — — — — — — ✅ Answer Console → 0 UI → 3 🧠 Why? React batches state updates and treats them as async. All setCount calls use the same stale value (count = 0). So internally: 0 + 1 = 1 0 + 2 = 2 0 + 3 = 3 ✅ (last update wins) 🔥 Correct way (if you want cumulative updates): setCount(prev => prev + 1); setCount(prev => prev + 1); setCount(prev => prev + 1); 👉 Now React updates sequentially → Final = 3 💬 Takeaway: • State updates are async • React batches updates • Avoid stale values • Use functional updates when chaining Did you get it right? 👀 #ReactJS #FrontendInterview #JavaScript #ReactHooks #FrontendDeveloper

React Interview Question: How do you handle long-running tasks in React without blocking the UI? In React, heavy computations or long-running tasks can freeze the UI because JavaScript runs on a single thread. Here are some effective techniques to handle long-running tasks without blocking the UI: 🔹 1. Use Web Workers (Best for heavy computations) Run expensive logic in a separate thread so the main UI thread stays free. This is Ideal for Data processing , Large calculations and Parsing big files 🔹 2. Break Work into Smaller Chunks Instead of one big blocking task, split it using: - setTimeout - requestIdleCallback This allows the browser to update the UI between tasks. 🔹 3. Use React Features (Concurrent UI) React provides tools to keep UI smooth: - useTransition (mark updates as non-urgent) - useDeferredValue (delay expensive rendering) 🔹 4. Memoization useMemo is used to cache expensive calculations useCallback is used to prevent unnecessary re-renders 🔹 5. Move Work to Backend If the computation is too heavy, move it to the backend: - offload processing to APIs - process tasks asynchronously on the server 🔹 6. Lazy Loading & Code Splitting Load only what’s needed using: - React.lazy - Suspense Connect/Follow Tarun Kumar for more tech content and interview prep #ReactJS #Frontend #WebDevelopment #JavaScript #InterviewPrep

🚀 React Interview Question: What is Lazy Loading in React? 💡 Lazy loading is a technique where components are loaded only when they are needed, instead of loading everything upfront. This helps improve performance and reduces initial load time. 🔹 How it works: Instead of importing components normally: import Dashboard from "./Dashboard"; You load them dynamically: const Dashboard = React.lazy(() => import("./Dashboard")); And wrap with Suspense: <Suspense fallback={Loading...}> 🔹 Why use Lazy Loading - faster initial page load - reduces bundle size - improves user experience 🔹 Real-world use case: Imagine a large app with multiple pages (Dashboard, Profile, Settings). Users don’t need all pages at once. - load only what the user visits. 🔹 Key Insight: - don’t load everything upfront. - load only when required. Connect/Follow Tarun Kumar for more tech content and interview prep 🚀 #ReactJS #Frontend #WebDevelopment #Performance #JavaScript #CodingInterview

🚀 Frontend / Full Stack Interview Experience (2.9 Years) Recently appeared for an interview and it was a good learning experience covering both fundamentals and practical concepts. 🔹 Key areas covered: 🧠 JavaScript Fundamentals • Event Loop & Execution Context • Closures and memory management • let vs var vs const • call, bind, and apply • How valueOf() works in JavaScript • setTimeout vs setImmediate • async/await and handling asynchronous operations • 5+ JavaScript output-based questions ⚡ Performance & Optimization • Debouncing vs Throttling • Image optimization techniques • Detecting and preventing memory leaks • Optimizing React applications • Optimizing API calls and handling large data efficiently • Next.js optimizations (code splitting, image optimization, caching) ⚛️ React & Rendering • Different rendering strategies (CSR, SSR, SSG) • Next.js Page Router vs App Router 🔌 Backend & System Concepts • Node.js fundamentals • WebSockets • MongoDB queries • Clustering basics A great learning experience — will keep building and improving. #FrontendDeveloper #ReactJS #NextJS #JavaScript #NodeJS #WebDevelopment #InterviewExperience #SoftwareEngineer

Job Trackr is a full-stack web app I built to make the job search process more organized and easier to manage created by Konstantinos Platias. It allows you to track your job applications, follow their progress, manage interviews, and keep notes—all in one simple dashboard. Live at: https://lnkd.in/dPR7wgZa This project has been a great way for me to strengthen my full-stack skills, working with: • React + TypeScript + Material UI (frontend) • Node.js + Express (backend) • SQL (Neon) for data management • Google OAuth (Passport.js) for authentication • Resend for email verification I’ll keep improving it and adding new features over time. Feedback is always welcome! #webdevelopment #fullstack #react #nodejs #projects #softwareengineering

Recently, I interviewed for multiple Senior React.js & Tech Lead roles — and noticed a pattern. Most interviewers asked basic but frequently repeated questions that test your clarity of concepts + coding approach. Here are the Top 10 common questions I was asked 👇 1️⃣ Call, Apply, Bind → Difference + Polyfill implementation 2️⃣ Flatten an Array without Array.flat() 👉 Input: [1,2,3,[4,5,6,[7,8,[10,11]]],9] 👉 Output: [1,2,3,4,5,6,7,8,10,11,9] 3️⃣ Inline 5 divs in a row without flex/margin/padding (Hint: display: inline-block) 4️⃣ Find sum of numbers without a for loop (Hint: reduce() / recursion) 5️⃣ Deep Copy vs Shallow Copy — behavior & how to achieve it 6️⃣ Promise & Async/Await output puzzle 7️⃣ Find first repeating character (e.g., "success" → "c") 8️⃣ Stopwatch Implementation (Start, Stop, Reset + live timer) 9️⃣ Build a To-Do List (Vanilla JS/React) → optimize re-renders 🔟 Currying for Infinite Sum 👉 sum(10)(20)(30)() → 60 👉 sum(10)(20)(30)(40)(50)(60)() → 210 𝐠𝐞𝐭 𝐞𝐛𝐨𝐨𝐤 𝐰𝐢𝐭𝐡 (detailed 232 ques = 90+ frequently asked Javascript interview questions and answers, 70+ Reactjs Frequent Ques & Answers, 50+ Output based ques & ans, 23+ Coding Questions & ans, 2 Machine coding ques & ans) 𝐄𝐛𝐨𝐨𝐤 𝐋𝐢𝐧𝐤: https://lnkd.in/gJMmH-PF Follow on Instagram : https://lnkd.in/gXTrcaKP #javascript #javascriptdeveloper #reactjs #reactnative #vuejsdeveloper #angular #angulardeveloper

Day 23 of my Interview Prep Series — Next.js Next.js isn't just a frontend framework anymore. Here are the questions you NEED to nail for full stack roles: 🔹 RENDERING & DATA FETCHING What's the difference between SSR, SSG, and ISR — and how do you decide which to use in a real app? 🔹 APP ROUTER How does layout.tsx work with nested routes? What's the difference between Server Components and Client Components, and when do you use each? 🔹 API & BACKEND How do Route Handlers work in the App Router? How would you handle authentication in a Next.js API route securely? 🔹 DATABASE INTEGRATION How do you connect a database (e.g. Prisma + PostgreSQL) in a Next.js app without leaking credentials to the client? 🔹 MIDDLEWARE & AUTH What can Next.js middleware do? Walk me through protecting a route with middleware using NextAuth or JWT. 🔹 PERFORMANCE How do dynamic imports, the Image component, and the font optimization system work together to improve Core Web Vitals? 🔹 DEPLOYMENT What happens under the hood when you deploy a Next.js app to Vercel vs a custom Node server? What's the difference? Full stack interviews test both ends — make sure your answers connect the frontend decision to the backend consequence. Drop your answers or questions below 👇 Let's build together. #NextJS #FullStackDeveloper #InterviewPrep #WebDevelopment #ReactJS #NodeJS #100DaysOfCode #TechCareers #JavaScript #Prisma

🚨 Stop Scrolling. This React Notes Can Save Your Next Interview. Most developers spend months learning React… But still fail interviews because they miss the right concepts. ❌ Random tutorials ❌ No structured revision ❌ Confusion in basics I was stuck in the same loop. So I created something simple 👇 🔥 50+ React Interview Questions + Concepts (All in One PDF) 💡 What’s inside: • React basics (JSX, Virtual DOM, Keys) • State vs Props (clear & interview-ready) • Hooks (useState, useEffect, useReducer, useMemo) • Routing + State Management (React Router, Redux) • Advanced topics (HOC, Context, Refs, Portals) • Performance optimization (memo, lazy loading) 👉 Everything explained in a short + easy revision format 👉 Perfect for last-minute interview prep 👉 No fluff. Only what actually matters. ⚡ I wish I had this earlier. It would have saved me weeks. If you’re learning React right now, this will help you a lot. 🔥 SAVE this post (you’ll need it later) ♻️ REPOST to help other developers 👨💻 Follow me for daily MERN content 💬 Comment "REACT" and I’ll share more advanced resources. #reactjs #javascript #webdevelopment #frontenddeveloper #mernstack

🚨 Stop Scrolling. This React Notes Can Save Your Next Interview. Most developers spend months learning React… But still fail interviews because they miss the right concepts. ❌ Random tutorials ❌ No structured revision ❌ Confusion in basics I was stuck in the same loop. So I created something simple 👇 🔥 50+ React Interview Questions + Concepts (All in One PDF) 💡 What’s inside: • React basics (JSX, Virtual DOM, Keys) • State vs Props (clear & interview-ready) • Hooks (useState, useEffect, useReducer, useMemo) • Routing + State Management (React Router, Redux) • Advanced topics (HOC, Context, Refs, Portals) • Performance optimization (memo, lazy loading) 👉 Everything explained in a short + easy revision format 👉 Perfect for last-minute interview prep 👉 No fluff. Only what actually matters. ⚡ I wish I had this earlier. It would have saved me weeks. If you’re learning React right now, this will help you a lot. 🔥 SAVE this post (you’ll need it later) ♻️ REPOST to help other developers 👨💻 Follow me for daily MERN content 💬 Comment "REACT" and I’ll share more advanced resources. #reactjs #javascript #webdevelopment #frontenddeveloper #mernstack