Tarun Kumar’s Post

Preparing for a Mid Level React Interview? Here’s another set of questions: => What is reconciliation in React and how does it work? => How does React decide when to re render components? => What is the Virtual DOM and how is it different from the real DOM? => How does it improve performance? => What are keys in React and why are they important? => What issues can arise from using index as a key? => What is prop drilling and how do you avoid it? => What are better alternatives? => How do you handle side effects in React applications? => What are common mistakes with useEffect? => What is code splitting and how do you implement it in React? => When should you use lazy loading? => What are custom hooks? => How do you design reusable hooks? => What is the difference between controlled and uncontrolled side effects? => How do you manage cleanup in components? => How do you handle error boundaries in React? => What are their limitations? => What is hydration in React? => When does it matter? => How do you manage forms in large scale applications? => What libraries or approaches would you use? => What is the difference between client side rendering and server side rendering? => What are the trade offs? => How do you optimize bundle size in a React app? => What tools would you use to analyze it? => What are common performance bottlenecks in React apps? => How do you identify and fix them? => How do you manage state synchronization between multiple components? => What challenges have you faced? => How do you handle race conditions in API calls in React? => How do you cancel stale requests? => How do you structure reusable and maintainable component libraries? => What patterns do you follow? #ReactJS #FrontendDevelopment #TechInterviews #JavaScript #WebDevelopment #Developers

Day 2 of Interview Prep Series 👇 ❓ Virtual DOM vs Real DOM — what’s the actual difference? Almost every React developer has heard this… But very few can explain it clearly in interviews. 💭 Try answering before scrolling 👇 . . . ✅ Real DOM • Direct representation of UI in the browser • Updating it is slow (re-renders entire tree) • Every change impacts performance ✅ Virtual DOM • A lightweight copy of the Real DOM • React updates this first • Uses a diffing algorithm to update only what changed 💡 In simple terms: Virtual DOM = smart updates Real DOM = direct updates That’s why React apps feel faster ⚡ 👉 Follow-up: Can you explain this with a real-world example? (That’s what actually impresses in interviews 👀) #Day2 #ReactJS #InterviewPrep #Frontend #Developers #Braintech #Learning

React Interview Guide: Components — From Basic to Advanced to Expert I created a detailed interview PDF guide covering one of the most important foundations of React: Components. This guide covers: ✅ Functional vs Class Components ✅ Props and PropTypes ✅ Component Composition ✅ Children Prop in React ✅ Basic to Advanced to Expert-level concepts ✅ Interview questions with answers ✅ Coding examples and practical scenarios React is component-driven, and understanding components deeply can make a big difference in interviews, real-world projects, and frontend architecture. Whether you are preparing for interviews, improving your React fundamentals, or revising before switching jobs, this guide can help you build clarity step by step. 📌 Topic: React Components 📄 Format: Interview PDF Guide 🎯 Level: Beginner → Advanced → Expert Happy learning and keep building! 🚀 #ReactJS #React #JavaScript #FrontendDevelopment #WebDevelopment #FrontendDeveloper #SoftwareEngineer #InterviewPreparation #CodingInterview #ReactDeveloper #JavaScriptDeveloper #TechInterview #Programming #LearnReact #DeveloperCommunity #100DaysOfCode #WebDev #CareerGrowth #SoftwareDevelopment #Components #Props #ReactInterview

🚀 Coding Interview Question: Prime Factorization (Must Know!) If you're preparing for DSA / Frontend / Fullstack interviews, this is a classic question you should not miss 👇 👉 Problem Statement: Given a positive integer "n", return its prime factorization: - Include all prime factors - Repeat factors based on multiplicity - Output in non-decreasing order - Format: list-like string 📌 Example: Input: 12 Output: [2, 2, 3] 💡 Approach: - Start dividing "n" from 2 - Keep dividing until it is no longer divisible - Move to next number - Continue till "n > 1" 💻 JavaScript Solution: function primeFactors(n) { let result = []; for (let i = 2; i * i <= n; i++) { while (n % i === 0) { result.push(i); n = n / i; } } if (n > 1) { result.push(n); } return `[${result.join(', ')}]`; } // Example console.log(primeFactors(12)); // [2, 2, 3] 🔥 Why this question is important? - Tests loops + logic building - Checks number theory basics - Evaluates edge case handling - Common in coding rounds ⚡ Pro Tip: Iterate till √n instead of n → better performance 💬 Have you faced this in interviews? Comment “YES” and I’ll share more tricky questions 👇 #javascript #reactjs #frontend #codinginterview #dsa #webdevelopment #softwareengineer #100DaysOfCode

Frontend Interview Series: The useEffect Dependency Array ⚛️ One of the most common sources of bugs in React is a misunderstood useEffect dependency array. It’s a favorite topic for interviewers to test your understanding of React's rendering lifecycle. The Breakdown: 1️⃣ No Array: useEffect(() => { ... }) Runs after every single render. If you perform a state update inside here without a condition, you’ll hit an infinite loop. ⚠️ 2️⃣ Empty Array: useEffect(() => { ... }, []) Runs only once after the initial mount. It’s the go-to choice for API calls or initializing subscriptions. ✅ 3️⃣ With Dependencies: useEffect(() => { ... }, [userId]) Runs on mount and whenever userId changes. React uses Shallow Comparison to decide if it should re-run the effect. The Interview Trap: Objects & Arrays 💡 In JavaScript, objects are compared by reference, not value. Even if the data is the same, a new object reference on every render will trigger the effect every single time! Understanding these small details is what helps in writing optimized React components. #ReactJS #JavaScript #FrontendDevelopment #WebDevelopment #InterviewPrep #CodingTips #SoftwareEngineering #LearningInPublic

🚨 Still preparing for React interviews the hard way? Most developers: ❌ Watch random tutorials ❌ Google the same questions again & again ❌ Forget concepts during interviews And that’s exactly why they get rejected. So I fixed this 👇 I created a complete React Interview Questions & Answers PDF with 100+ real questions that actually get asked in interviews � React Interview Questions Answers📝 .pdf 💡 What’s inside? ✔ React fundamentals (JSX, Props, State) ✔ Hooks (useState, useEffect, useReducer, etc.) ✔ Virtual DOM & performance concepts ✔ Redux & state management ✔ Advanced topics (memo, refs, SSR, optimization) ✔ Real interview-level questions with answers 🎯 If you're a: → Beginner struggling with concepts → Developer preparing for interviews → MERN dev aiming for better opportunities This will save you hours of searching. 📌 Don’t just scroll… 👉 Save this post (you’ll need it later) 🔁 Repost to help other developers 💬 Comment “REACT” and I’ll share more resources 🔥 Follow me for: Daily dev content Real interview prep MERN roadmap & resources #reactjs #webdevelopment #frontenddeveloper #mernstack #javascript #coding #developers #programming #techcareer #interviewprep #softwaredeveloper #100DaysOfCode

🚀 React Interview Question: What is the useRef hook and when should you use it? 💡In React, useRef is a hook that lets you store values that persist across renders — without triggering a re-render. 🔹 Key Idea: useRef returns a mutable object with a .current property that you can update anytime. 🔹 Use cases: Access DOM Elements - perfect for focusing inputs, scrolling, or measuring elements. Store Mutable Values - keep values like counters, timers, or flags without re-rendering. Persist Previous Values - track previous state or props easily. 💡 Interview Tip: useRef is used to persist values across renders without triggering re-renders and is commonly used for DOM access and storing mutable values. Follow Tarun Kumar for tech content, coding tips, and interview prep #React #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #CodingInterview #InterviewPreparation #SoftwareEngineering #TechLearning #Programming

📌 Want to clear JavaScript interviews in 2026? Don’t skip these questions. If you're preparing for Frontend / SDE interviews, these are MUST-know concepts 👇 1. What is hoisting in JavaScript? 2. Difference between var, let, const 3. What is closure? 4. Explain this keyword behavior 5. Difference between == vs === 6. What is event loop? 7. What are promises and async/await? 8. What is callback hell? 9. Difference between map, filter, reduce 10. What is debouncing vs throttling? 11. What is prototype & prototypal inheritance? 12. What is currying? 13. What is memoization? 14. Difference between deep copy vs shallow copy 15. What is IIFE (Immediately Invoked Function Expression)? 16. What is setTimeout vs setInterval? 17. What is null vs undefined? 18. How does JavaScript handle memory (garbage collection)? 19. What are ES6 features you use daily? 20. What is module system (CommonJS vs ES Modules)? 💡 Pro Tip: Don’t just memorize answers — practice explaining with examples. That’s what interviewers look for. 📌 Save this post & revise before interviews! Don't forget to like this post Hrithik Garg 🚀 for more frontend interview content. #javascript #frontend #webdevelopment #interviewpreparation #coding #developers

React Components Interview Q&A Guide — Basic to Expert Level I created a complete React Components Interview Guide in Q&A format, covering concepts from beginner to expert level. This guide includes: ✅ Functional Components ✅ Props and Children ✅ Component Composition ✅ State and Re-rendering ✅ Controlled vs Uncontrolled Components ✅ Memoization and Performance ✅ Refs and Forwarding Refs ✅ Error Boundaries ✅ Suspense and Lazy Loading ✅ Server vs Client Components ✅ Common Edge Cases ✅ Interview-style Questions & Answers React components look simple at first, but many interview questions test deeper understanding: “How does React preserve state?” “When does a component re-render?” “Why should keys be stable?” “What is the real use of children?” “When should we avoid memo?” This guide is useful for: 🔹 Frontend Developers 🔹 React Learners 🔹 Interview Preparation 🔹 JavaScript Developers moving into React 🔹 Developers revising component-level architecture React is not just about writing JSX. Understanding components properly helps you write cleaner, reusable, scalable, and interview-ready frontend code. If you are preparing for React interviews, this can be a strong revision resource. #ReactJS #React #JavaScript #FrontendDevelopment #WebDevelopment #InterviewPreparation #ReactInterview #FrontendInterview #SoftwareDeveloper #SoftwareEngineering #JavaScriptDeveloper #CodingInterview #Programming #TechCareers #100DaysOfCode #DeveloperCommunity #WebDeveloper #UIEngineering #FrontendEngineer #LearnReact

🚀 Top 10 React Basic Interview Questions 🔹 1. What is useState? - > used to manage state in functional components const [count, setCount] = useState(0); 🔹 2. What is useEffect? -> handles side effects (API calls, subscriptions) useEffect(() => { console.log("Component Mounted"); }, []); 🔹 3. How to handle forms in React? (Controlled Components) const [input, setInput] = useState(""); <input value={input} onChange={e => setInput(e.target.value)} /> 🔹 4. How to fetch API data? useEffect(() => { fetch("/api") .then(res => res.json()) .then(data => console.log(data)); }, []); 🔹 5. What is conditional rendering? {isLoggedIn ? <Dashboard /> : <Login />} 🔹 6. How to pass data from parent to child? <Child name="Test" /> 🔹 7. How to optimize performance? (React.memo) export default React.memo(Component); 🔹 8. What is useCallback? -> memoizes functions const handleClick = useCallback(() => {}, []); 🔹 9. What is useMemo? -> memoizes values const value = useMemo(() => compute(), []); 🔹 10. How to handle list rendering? items.map(item => <li key={item.id}>{item.name}</li>); ✅ If you are preparing for ReactJs interview, save this for your next interview! 👉 Follow Tarun Kumar for tech content, coding tips, and interview prep 🚀 #ReactJS #FrontendDeveloper #JavaScript #WebDevelopment #CodingInterview #SoftwareEngineer #TechCareers #LearnReact