React Strict Mode: Early Bug Detection in Development

🚀 React Interview Question: What is Code Splitting in React? 💡 Code Splitting is a technique used to split your React application into smaller bundles so that only the required code is loaded when needed. Instead of loading the entire app at once, React loads parts of the app on demand. 🔹 Why do we need it? Sometimes in large applications: - bundle size becomes very big - initial load time increases - performance becomes slow Code Splitting helps load only what is necessary, improving performance. 🔹 How does it work? React provides lazy loading using React.lazy() and Suspense. 🔹Example: import React, { Suspense } from "react"; const Dashboard = React.lazy(() => import("./Dashboard")); function App() { return ( <div> <h1>My App</h1> <Suspense fallback={<p>Loading...</p>}> <Dashboard /> </Suspense> </div> ); } export default App; here, the Dashboard component is loaded only when needed, not in the initial bundle. 🔹 Benefits of Code Splitting - reduces initial load time - improves performance - loads components on demand - better user experience 🔹 Use case: In large applications with multiple pages (like dashboards or admin panels), you don’t need to load everything at once. With code splitting, each page is loaded only when the user navigates to it, improving performance and reducing initial load time. Connect/Follow Tarun Kumar for more tech content and interview prep #React #JavaScript #Frontend #WebDevelopment #Performance #Coding #SoftwareEngineering #InterviewPrep

React Interview Question: What is Concurrent Mode in React & Why It Matters? React apps may become slow during heavy updates since all rendering happens on a single thread. To solve this, React 18 introduces Concurrent Features (previously experimented as Concurrent Mode). 🔹 What is Concurrent Mode? Concurrent Features allow React to pause, resume, and prioritize rendering work as needed. Instead of blocking the UI, React becomes more flexible and responsive. 🔹 How Concurrent Mode improves performance? Interruptible rendering - React can pause rendering work in between and resume later instead of blocking the main thread. Incremental rendering (breaking work into chunks) - Large rendering tasks are split into smaller units so the browser gets time to handle user interactions. Priority-based scheduling - Updates are assigned priorities (e.g., user input > data rendering), ensuring critical work runs first. Avoiding unnecessary work - React can discard outdated renders if newer updates come in, preventing wasted computation. 🔹 Key features behind it  useTransition ( Mark updates as non-urgent )  useDeferredValue ( Delay rendering of less important data )  Automatic batching ( Fewer re-renders — a React 18 improvement, works independently of concurrent features ) 🔹 Example const [isPending, startTransition] = useTransition(); const handleChange = (e) => {  const value = e.target.value;  setInput(value); // urgent update  startTransition(() => {   setFilteredList(filterItems(value)); // non-urgent  }); }; 🔹Conclusion Concurrent Features in React 18 make apps faster, smoother, and more responsive by scheduling and prioritizing rendering tasks efficiently. Connect/Follow Tarun Kumar for more tech content and interview prep #React #Frontend #WebDevelopment #JavaScript #Performance #SoftwareEngineering

🚀 React Interview Question:What is forwardRef() in React used for? 💡 What is forwardRef()? forwardRef is a React utility that allows a parent component to pass a ref through a child component, enabling direct access to the child’s DOM node or instance. This is especially useful when the child is wrapped by other components and doesn’t expose the ref by default. - by default, refs don’t work on custom components - forwardRef makes it possible 🔹 Why do we need it? Sometimes we need direct DOM access for: - focusing an input - triggering animations - integrating with third-party libraries 🔹 Example: import React, { forwardRef } from "react"; const Input = forwardRef((props, ref) => { return <input ref={ref} {...props} />; }); export default function App() { const inputRef = React.useRef(); return ( <> <Input ref={inputRef} /> <button onClick={() => inputRef.current.focus()}> Focus Input </button> </> ); } 🔹 When should you use forwardRef()? - when parent needs direct access to child DOM - for reusable component libraries - for focus, scroll, or animations - when integrating non-React code Follow Tarun Kumar for tech content, coding tips, and interview prep #React #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #CodingInterview #InterviewPreparation #SoftwareEngineering #TechLearning #Programming

Some of the most commonly asked questions in React interviews in 2026 that might help fellow developers preparing for similar roles. 💡 🔍 Key React Interview Questions (2026 Trends) 1️⃣ What are the differences between Client Components and Server Components in React? 2️⃣ Explain the React rendering lifecycle in functional components. 3️⃣ How does React Fiber architecture improve performance? 4️⃣ What are custom hooks and when should you create one? 5️⃣ Difference between useMemo, useCallback, and React.memo. 6️⃣ How does React handle reconciliation and the virtual DOM? 7️⃣ What are controlled vs uncontrolled components? 8️⃣ How would you optimize a React application experiencing unnecessary re-renders? 9️⃣ Explain state management approaches (Context API, Redux, Zustand, etc.). 🔟 What are React Server Components and how do they impact performance? ⚙️ Practical / Coding Round Topics • Build a searchable list with debouncing • Create a custom hook (e.g., useDebounce / useFetch) • Implement pagination or infinite scrolling • Optimize a component suffering from performance issues • Implement form validation in React 💬 Behavioral / System Thinking Questions • How do you structure a scalable React project? • How do you handle performance optimization in large React apps? • Explain a challenging bug you solved in production. ✨ Key Takeaway: Companies are increasingly focusing on React internals, performance optimization, hooks, and real-world architecture decisions, rather than just basic syntax. If you're preparing for a React Developer role in 2026, focus on: ✔ Hooks & custom hooks ✔ Performance optimization ✔ Modern React architecture ✔ Real-world problem solving Hope this helps someone preparing for their next opportunity! 🙌 #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #ReactDeveloper #FrontendEngineer #SoftwareEngineering #TechInterviews #InterviewPreparation #ProductBasedCompany #ReactHooks #Programming

React Interview Question: How does React Router work, and how do you implement dynamic routing? 🔹 How React Router works React Router is a client-side routing library that enables navigation between components without reloading the page. Instead of requesting a new HTML page from the server, React Router: - listens to URL changes - matches the URL with a defined route - renders the corresponding component - updates UI without full page refresh This makes React apps fast and seamless. 🔹 What is Dynamic Routing? Dynamic routing means routes are not fixed, they change based on parameters in the URL. Example of Dynamic Routing: /user/1 /user/2 /product/101 Here, 1, 2, 101 are dynamic values. 🔹 How to implement Dynamic Routing in React We use route parameters using : (colon syntax). Example: import { BrowserRouter, Routes, Route, useParams } from "react-router-dom"; function User() { const { id } = useParams(); return <h2>User ID: {id}</h2>; } function App() { return ( <BrowserRouter> <Routes> <Route path="/" element={<h1>Home</h1>} /> <Route path="/user/:id" element={<User />} /> </Routes> </BrowserRouter> ); } 🔹 How it works internally - user visits /user/5 - react Router matches /user/:id - extracts id = 5 - passes it to component via useParams() - component renders dynamic data 🔹 Real-world use cases - user profile pages - product detail pages - order details - blog post pages 🔹Conclusion: React Router enables SPA navigation, and dynamic routing allows you to build flexible, data-driven pages using URL parameters. Connect/Follow Tarun Kumar for more tech content and interview prep #ReactJS #ReactRouter #FrontendDevelopment #JavaScript

💼 Frontend Interview Experience – Round 1 Recently, I went through the first round of a frontend interview. Sharing the questions I was asked - this round focused heavily on performance, React internals, and real-world scenarios. 🟡 Core Frontend & Performance: 1️⃣ How do you optimize performance of an application? 2️⃣ What is lazy loading? 3️⃣ How to cancel previous API requests? 4️⃣ Difference between SSR and CSR? 5️⃣ What is WebSocket? 6️⃣ What is Service Worker? 7️⃣ How do you prevent XSS and CSRF attacks? 🟢 React & State Management: 8️⃣ Explain implementation of Context API? 9️⃣ Explain implementation of Redux Toolkit? 🔟 Difference between Redux and Redux Toolkit? 1️⃣1️⃣ What is useEffect? 1️⃣2️⃣ What are Error Boundaries? Explain implementation? 1️⃣3️⃣ How do you handle errors in React applications? 1️⃣4️⃣ What is reconciliation? 1️⃣5️⃣ Difference between React 16 and React 18? 1️⃣6️⃣ What is state scheduling? 🔵 JavaScript & Coding: 1️⃣7️⃣ What are closures? 1️⃣8️⃣ Implement throttle? 1️⃣9️⃣ Difference between fetch and axios? 2️⃣0️⃣ Write code to find frequency of elements in an array? 🟣 Practical / Scenario-Based: 2️⃣1️⃣ Why migrate from Angular to React? What challenges did you face? 2️⃣2️⃣ How to send data from parent to child component? 2️⃣3️⃣ What is prop drilling? 💭 Key takeaway: The interview focused a lot on real-world problem solving, performance optimization, and deep understanding of React concepts rather than just theory. Preparing fundamentals + practical scenarios is the key 🔑 #frontenddevelopment #reactjs #javascript #interviewexperience

Day 25/30 — Next.js Interview Prep "How do you optimize performance in a Next.js app?" (This question separates mid-level from senior developers) Most devs build Next.js apps that work. But interviewers want to know — can you make them fast? Here are 5 performance optimization techniques you must know: 1️⃣ Use the <Image> Component Never use a raw <img> tag in Next.js. The built-in Image component gives you lazy loading, WebP format, and automatic resizing — out of the box. 2️⃣ Code Splitting with dynamic() Don't load what the user doesn't need yet. Use dynamic() to import heavy components only when they're needed. → Smaller bundle = faster load time. 3️⃣ Choose the Right Data Fetching Strategy getStaticProps → for content that rarely changes getServerSideProps → for real-time data ISR (revalidate) → best of both worlds Most candidates get this wrong in interviews. Know when to use each. 4️⃣ Optimize Fonts & Scripts Use next/font to eliminate layout shift. Use next/script to control when third-party scripts load. These two alone can boost your Lighthouse score significantly. 5️⃣ Caching with revalidate Set a revalidation time on static pages so your app serves cached content fast — and refreshes in the background silently. Performance optimization = the skill that gets you hired at top companies. 💬 Which of these did you already know? Drop a number (1–5) in the comments! Follow me for Day 26 tomorrow — we're diving into MERN stack system design questions. 🔥 #NextJS #WebDevelopment #InterviewPrep #JavaScript #100DaysOfCode #LinkedInTech #MERNStack #SoftwareEngineering #FrontendDevelopment #TechTwitter

🚀 React Interview Question: What are Error Boundaries in React? 💡 Error Boundaries: Error Boundaries are components that catch errors in the UI and prevent the app from crashing. Instead of showing a broken screen, they display a fallback UI like “Something went wrong.” 🔹 Why use them? - prevent full app crash - show user-friendly error message - improve user experience 🔹 Example: class ErrorBoundary extends React.Component { state = { hasError: false }; static getDerivedStateFromError() { return { hasError: true }; } render() { if (this.state.hasError) { return <h1>Something went wrong </h1>; } return this.props.children; } } 🔹Note: Error Boundaries only work in class components ✅ If you are preparing for ReactJs interview, save this for your next interview! Follow Tarun Kumar for tech content, coding tips, and interview prep 🚀 #React #JavaScript #InterviewPrep #Frontend #Coding

🚀 Next.js Interview Prep – What Really Matters I used to think learning React was enough… But when I started preparing for interviews, I realized how important Next.js has become in modern frontend development. Here are some must-know concepts every developer should master 👇 ✅ SSR, SSG, ISR – Know when and why to use each ✅ App Router vs Pages Router – Understand the new architecture ✅ Server vs Client Components – Performance + scalability ✅ Data Fetching – fetch(), async/await, caching strategies ✅ Authentication (NextAuth) – Real-world secure apps ✅ Middleware – Handling redirects, auth & edge logic ✅ Image Optimization – Using next/image properly ✅ Performance – Bundle size, lazy loading, code splitting 💡 Big realization: In interviews, it's not about definitions — it's about explaining real-world use cases + trade-offs 🎯 Interview Questions You Should Practice: When would you use SSR vs SSG vs ISR? What is the difference between App Router and Pages Router? How do Server Components improve performance? How does data fetching work in Next.js 13+? How would you implement authentication in Next.js? What is middleware and where is it used? How do you optimize images and performance? How to reduce bundle size in a Next.js app? 🔥 Pro Tip: Don’t just learn concepts — 👉 Build projects, break things, fix them 👉 That’s what makes you interview-ready #Nextjs #React #FrontendDevelopment #WebDevelopment #InterviewPreparation #Developers #Coding

🚀 React Interview Question: How to create and use Custom Hooks in React? 💡 A Custom Hook in React is a reusable function that lets you extract and share logic across components. Instead of duplicating logic (like API calls, form handling, or event listeners), you can move it into a custom hook and reuse it anywhere. 🔹 Why use Custom Hooks? - reusability - cleaner components - better separation of concerns - easier testing & maintenance 🔹 How to create a Custom Hook? - create a function starting with use import { useState, useEffect } from "react"; function useFetch(url) { const [data, setData] = useState(null); useEffect(() => { fetch(url) .then(res => res.json()) .then(data => setData(data)); }, [url]); return data; } 🔹 How to use it in a component? function Users() { const data = useFetch("https://lnkd.in/gxkxVfEt"); return ( <div> {data ? data.map(user => <p key={user.id}>{user.name}</p>) : "Loading..."} </div> ); } 🔹 Key Rules - always start with use - can use other hooks inside (useState, useEffect, etc.) - must follow React Hook rules Follow Tarun Kumar for more tech content and interview prep #ReactJS #CustomHooks #FrontendDevelopment #JavaScript #WebDevelopment #CodingInterview #SoftwareEngineering #TechContent #Developers