Kunal Thakur’s Post

🚀 Top 30 MUST-KNOW Frontend Interview Questions If you're preparing for your next frontend role, these are the questions that keep showing up. Not just theory — these test how you think, build, and debug in real-world scenarios. 👉 Challenge yourself: How many can you confidently answer without Googling? 🔥 Core JavaScript ① What is the difference between == and ===? ② Explain closures with a practical example. ③ How does the event loop work? ④ What are promises vs async/await? ⑤ What is hoisting? ⑥ Explain prototypal inheritance. ⑦ What are higher-order functions? ⑧ What is debouncing vs throttling? ⚛️ React (or similar frameworks) ⑨ What happens during React’s rendering process? ⑩ Difference between state and props? ⑪ What are hooks? Why were they introduced? ⑫ Explain useEffect lifecycle behavior. ⑬ Controlled vs uncontrolled components? ⑭ What causes unnecessary re-renders? ⑮ How does React reconciliation work? ⑯ What is memoization (React.memo, useMemo, useCallback)? 🌐 Browser & Performance ⑰ How does the DOM work? ⑱ What is the difference between localStorage, sessionStorage, and cookies? ⑲ What is CORS and how does it work? ⑳ How can you optimize frontend performance? ㉑ What is lazy loading? ㉒ What happens when you type a URL in the browser? 🎨 HTML & CSS ㉓ Difference between display: none and visibility: hidden? ㉔ What is the box model? ㉕ Flexbox vs Grid — when to use which? ㉖ What are pseudo-classes vs pseudo-elements? ㉗ How does CSS specificity work? 🧠 Architecture & Best Practices ㉘ How do you structure a scalable frontend app? ㉙ What is code splitting? ㉚ How do you handle API errors and loading states? 💡 Pro Tip: Interviewers aren’t just checking answers — they’re evaluating: Your clarity of thought Real-world experience Ability to debug and optimize 🔥 Your turn: How many did you get confidently? Drop your score 👇 And tell me — which one do you find the trickiest? #FrontendDevelopment #JavaScript #ReactJS #WebDevelopment #FrontendEngineer #CodingInterview #TechCareers #SoftwareEngineering #InterviewPrep #Developers #LearnToCode #CareerGrowth

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

Frontend Interview Experience – A Small but Interesting Redux Debate Recently attended a frontend interview where the discussion covered HTML, CSS, JavaScript, React, GraphQL, and Microfrontends. During the React round, I was asked about the core pillars of Redux. I explained: • Store – holds the application state • Actions – plain JavaScript objects describing what happened • Reducers – pure functions that return the new state • Dispatch – sends actions to the store • Selectors – used to read data from the store Then came an interesting moment The interviewer mentioned that "Actions are functions, not objects." I respectfully shared my understanding that: In Redux, an Action is a plain JavaScript object with a mandatory type field. After the interview, I double-checked — and yes, Redux defines actions as plain objects. The likely confusion: What the interviewer referred to was Action Creators, which are functions that return action objects. Example: const addTodo = (text) => ({ type: "ADD_TODO", payload: text }); Key takeaway: • Action = Object • Action Creator = Function 🎯 Interviews are not just about right or wrong — they’re about clarity of concepts and communication. Curious to know — have you ever faced a situation where both perspectives were technically correct but misunderstood in interviews? #Frontend #React #Redux #JavaScript #InterviewExperience #Learning

❌ Got rejected in a Frontend interview — but learned something important. Frontend interviews aren’t really about React… they’re about how strong your JavaScript is. Recently went through a Frontend Developer interview process and here’s a round-wise breakdown with some of the most asked questions 👇 🔹 JavaScript (Most Important Round) This is where most candidates struggle. 1. What is closure? Where have you used it? 2. Explain event loop with execution order 3. Implement debounce/throttle in JavaScript 4. How does "this" behave in different contexts? 5. Promise chaining vs async/await 🔹 Round 2: React Deep Dive 1. Why do components re-render? 2. useMemo vs useCallback vs React.memo 3. How does useEffect lifecycle work? 4. How do you prevent unnecessary renders? 5. Real-world state management approach 🔹 Round 3: Machine Coding 1. Build a debounced search / autocomplete 2. Handle API calls with proper states 3. Focus on clean architecture & reusability 4. Edge cases + performance considerations 🔹 Round 4: Frontend System Design 1. Design a scalable UI (dashboard/feed) 2. Folder structure & code organization 3. API handling and caching 4. Performance optimization techniques 🔹 Round 5: Hiring Manager Round 1. Deep dive into your project 2. Why did you choose certain approaches 3. Challenges and trade-offs 4. Ownership and decision making 💡 Biggest takeaway: Frameworks change, but strong fundamentals stay. Don't forget to like this post and follow Hrithik Garg 🚀 for more :) #Frontend #JavaScript #React #InterviewExperience #WebDevelopment #SDE

After attending multiple frontend interviews over the past few years, I noticed a pattern — certain questions keep coming up again and again. If you're preparing for a Frontend Developer role (especially with 2-3 years experience), these are some of the most commonly asked questions: 🚀 React & Frontend • How does React reconciliation and Virtual DOM work? • Difference between useMemo and useCallback? • Context API vs Redux — when to use which? • How do you prevent unnecessary re-renders? • Explain lifecycle methods (or useEffect in hooks) • What are Higher Order Components? ⚡ JavaScript Core • Closures, hoisting, scope — explain with examples • Event loop (microtasks vs macrotasks) • Difference between == and === • call vs apply vs bind • Promises vs async/await 🌐 API & Performance • How do you handle API failures? • How do you optimize API calls? • What is debouncing and throttling? • Handling large datasets in frontend (pagination, virtualization) 🔐 System & Security • Authentication vs Authorization • What is JWT and how it works? • What is CORS? 🏗 Practical / Scenario-Based • How do you stop API calls on component unmount? • How would you handle millions of records in UI? • How do you improve performance in a React app? 💡 One key takeaway: Most interviews are not about memorizing answers — they focus on how you apply concepts in real projects. If you're preparing, focus on: ✔ Real-world examples ✔ Performance optimization ✔ Clear explanations Hope this helps someone preparing for frontend interviews! 🚀 #frontenddeveloper #reactjs #javascript #webdevelopment #interviewpreparation #softwareengineering

🚀 Most Asked React / React Native Interview Question (Must Prepare!) 💡 Most Important Concept: Arrow Function vs Normal Function + this keyword 👉 1. Normal Function js function greet() { console.log(this); } ✔ this depends on how the function is called ✔ Value can change dynamically 👉 2. Arrow Function js const greet = () => { console.log(this); } ✔ this is lexically bound (taken from parent scope) ✔ Cannot be changed using call, apply, bind 🎯 Key Difference (Interview Point) ⚡ Normal Function • Has its own this • Dynamic context • Used in object methods when context matters ⚡ Arrow Function • No own this • Uses surrounding this • Best for callbacks (clean & predictable) 🧠 Example (Must Remember) js const obj = { name: "React", normalFunc: function () { console.log(this.name); }, arrowFunc: () => { console.log(this.name); } }; obj.normalFunc(); // React ✅ obj.arrowFunc(); // undefined ❌ 👉 Why? Because arrow function does NOT bind this, it takes from outer scope. 🔥 Pro Interview Tip Use arrow functions when you don’t want this to change. Use normal functions when this should refer to the object. 💬 Save this post if you're preparing for interviews & want to revise quickly! #React #ReactNative #JavaScript #Frontend #InterviewPrep #Coding

Frontend interviews used to be mostly about frameworks — “what is React?”, hooks, lifecycle, etc. But recently, I noticed a shift Interviewers are digging deeper into 𝐫𝐞𝐚𝐥-𝐰𝐨𝐫𝐥𝐝 𝐩𝐞𝐫𝐟𝐨𝐫𝐦𝐚𝐧𝐜𝐞. 𝐐𝐮𝐞𝐬𝐭𝐢𝐨𝐧𝐬 𝐈’𝐯𝐞 𝐛𝐞𝐞𝐧 𝐚𝐬𝐤𝐞𝐝 (𝐨𝐫 𝐬𝐞𝐞𝐧 𝐛𝐞𝐢𝐧𝐠 𝐚𝐬𝐤𝐞𝐝): → What exactly is 𝐋𝐂𝐏 (Largest Contentful Paint) and why does it matter? → How would you improve 𝐋𝐂𝐏 on a slow-loading page? → Difference between 𝐋𝐂𝐏, 𝐅𝐂𝐏, and 𝐂𝐋𝐒? → How does lazy loading impact performance metrics? → What are render-blocking resources, and how do you handle them? → How does Next.js optimize performance out of the box? At first, you might think knowing definitions would be enough. It’s not. 𝐓𝐡𝐞𝐲 𝐞𝐱𝐩𝐞𝐜𝐭 𝐲𝐨𝐮 𝐭𝐨 𝐭𝐡𝐢𝐧𝐤 𝐥𝐢𝐤𝐞 𝐭𝐡𝐢𝐬: What’s slowing the page down? What’s visible to the user first? What can be deferred, optimized, or removed? 𝐁𝐢𝐠𝐠𝐞𝐬𝐭 𝐫𝐞𝐚𝐥𝐢𝐳𝐚𝐭𝐢𝐨𝐧: Performance is no longer a “nice to know” — it’s becoming a core frontend skill. You can build beautiful UIs… But if they load slow, it doesn’t matter. Even the platforms we use every day aren’t perfect — (attaching LinkedIn’s performance metrics, I observed 👇)

🔥 Most Developers FAIL Next.js Interviews… Not because they don’t know React — But because they don’t know how Next.js actually works in production. So I created something different 👇 📘 Next.js Interview Mastery (80 Questions — Basic → Advanced) This is not theory. This is what companies ACTUALLY ask. ✔ App Router vs Pages Router ✔ Server vs Client Components ✔ SSR vs SSG vs ISR (real use cases) ✔ Routing, Layouts, Middleware ✔ Performance & SEO ✔ Production patterns 👉 Everything explained with real code + interview tips 💡 Example (from the PDF): 👉 Next.js is not just React It gives: • Server-side rendering (better SEO) • File-based routing (no react-router) • API routes (backend inside frontend) • Image + font optimization 📌 That’s why companies prefer it over CRA 🔥 BONUS I’m also sharing my 950+ Full-Stack Interview Q&A PDF Covers: ✔ JavaScript (Core + Advanced) ✔ React ✔ Node.js ✔ MongoDB ✔ System Design ✔ Auth + Security ✔ Testing 🎯 HOW TO GET IT 💬 Comment: 👉 “FULLSTACK” → Get 950 Q&A PDF 👉 “NEXTJS” → Get Next.js 80 Q PDF 💾 Save this (you’ll need it before interviews) 🔁 Repost to help other devs 👨💻 Follow me Asif Ali Quraishi ♞ for daily interview prep

If you're a CS student preparing for technical interviews, this is worth a read. It breaks down exactly what actually matters across HTML, CSS, JavaScript, and React. I've been working through a lot of these concepts lately, and this is a great reference to keep coming back to. Sharing this because I wish I had found it sooner! 📌 #SoftwareEngineering #ComputerScience #TechCareers

🔥 Most Developers FAIL Next.js Interviews… Not because they don’t know React — But because they don’t know how Next.js actually works in production. So I created something different 👇 📘 Next.js Interview Mastery (80 Questions — Basic → Advanced) This is not theory. This is what companies ACTUALLY ask. ✔ App Router vs Pages Router ✔ Server vs Client Components ✔ SSR vs SSG vs ISR (real use cases) ✔ Routing, Layouts, Middleware ✔ Performance & SEO ✔ Production patterns 👉 Everything explained with real code + interview tips 💡 Example (from the PDF): 👉 Next.js is not just React It gives: • Server-side rendering (better SEO) • File-based routing (no react-router) • API routes (backend inside frontend) • Image + font optimization 📌 That’s why companies prefer it over CRA 🔥 BONUS I’m also sharing my 950+ Full-Stack Interview Q&A PDF Covers: ✔ JavaScript (Core + Advanced) ✔ React ✔ Node.js ✔ MongoDB ✔ System Design ✔ Auth + Security ✔ Testing 🎯 HOW TO GET IT 💬 Comment: 👉 “FULLSTACK” → Get 950 Q&A PDF 👉 “NEXTJS” → Get Next.js 80 Q PDF 💾 Save this (you’ll need it before interviews) 🔁 Repost to help other devs 👨💻 Follow me M. WASEEM ♾️ for daily interview prep