React State vs Props: Understanding the Difference

Headline: 🚀 Master Your Next React Interview: 100 Questions from Junior to Expert Preparing for a React interview can feel like trying to hit a moving target. Whether you're just starting with useState or architecting complex systems with Fiber and Server Components, you need a roadmap. I’ve compiled a comprehensive list of 100 React JS Interview Questions, categorized by difficulty, to help you (or your team) level up. 🔹 Junior: Fundamentals, JSX, and Hooks. 🔹 Intermediate: Performance, Patterns, and Logic. 🔹 Senior: Architecture, Testing, and SSR. 🔹 Expert: React Internals, Fiber, and System Design. Check out the list below and save this for your next prep session! Which of these would you find hardest to answer on the spot? 👇 #ReactJS #WebDevelopment #Frontend #CodingInterview #JavaScript #CareerGrowth

👉 “What are the Rules of React Hooks?” Day26 If you’re preparing for React interviews, this is a MUST-know topic. ✅ The 3 Main Rules: 1️⃣ Only Call Hooks at the Top Level ❌ Not inside loops ❌ Not inside conditions ❌ Not inside nested functions 2️⃣ Only Call Hooks from React Functions ✅ Functional Components ✅ Custom Hooks ❌ Not inside regular JS functions ❌ Not inside class components 3️⃣ Hook Order Must Stay the Same React depends on the order of Hook calls to manage state correctly. 💡 Why is this important? Because React tracks Hooks based on their call order. If the order changes → state breaks → bugs appear. 🎯 Interview Tip: “Hooks must always be called at the top level of a functional component or custom hook, and their order should never change.” Mastering fundamentals like this makes you a stronger React developer 💪 👨💻 Follow for daily React, and JavaScript 👉 Arun Dubey What React topic should I explain next? 👇 #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #ReactHooks #InterviewPreparation #Day26

🚀 #100DaysOfCode – Day 2 ⚠️ This one concept breaks most JavaScript interviews: ✨ Closures 👀 Look at this: for (var i = 1; i <= 3; i++) { setTimeout(() => console.log(i), 1000); } ❓ What do you expect? → "1 2 3" 😬 What you get? → "4 4 4" 🧠 What’s happening? Closures don’t copy values… they remember variables. And "var" shares the same scope. ✅ Fix (modern JS) for (let i = 1; i <= 3; i++) { setTimeout(() => console.log(i), 1000); } 💡 In one line: Closure = function + memory of its outer scope 🔥 Why you should care? → React hooks → Event handlers → Almost every serious JS interview #JavaScript #FrontendDeveloper #100DaysOfCode #WebDevelopment

𝐑𝐞𝐚𝐜𝐭 𝐮𝐬𝐞𝐄𝐟𝐟𝐞𝐜𝐭 𝐈𝐧𝐟𝐢𝐧𝐢𝐭𝐞 𝐋𝐨𝐨𝐩 𝐈𝐧𝐭𝐞𝐫𝐯𝐢𝐞𝐰 𝐐𝐮𝐞𝐬𝐭𝐢𝐨𝐧 🚨 Many React developers face this problem… but can’t explain why it happens in interview. Question: Why does useEffect cause infinite loop sometimes? Example ❌ const [count, setCount] = useState(0); useEffect(() => { setCount(count + 1); }, [count]); What happens here? ➡ count changes ➡ useEffect runs ➡ setCount updates state ➡ state change triggers useEffect again ➡ loop continues forever This creates an infinite re-render loop. Correct way ✅ useEffect(() => { setCount(prev => prev + 1); }, []); Why this works? Because empty dependency array runs useEffect only once. Tip for React Interviews: Always check dependency array carefully. Most infinite loop bugs come from wrong dependencies. More React interview questions coming 🚀 #ReactJS #useEffect #FrontendDeveloper #JavaScript #WebDevelopment #CodingInterview #ReactInterview #NextJS #SoftwareDeveloper

I compiled a small JavaScript + React interview questions for quick revision. It includes common frontend interview topics with questions, answers, and short explanations, such as: • Hoisting, Closures, Event Loop • Promises, Microtasks vs Macrotasks • Virtual DOM & Reconciliation • React Hooks and performance concepts • CSR vs SSR and Hydration Sharing it in case it helps someone preparing for frontend interviews. #javascript #reactjs #FrontendDevelopment #InterviewPreparation #SoftwareEngineering

⚛️ Stop Learning React the Wrong Way Most developers focus on syntax. But interviews test understanding. You’re preparing for React interviews in 2026, these concepts matter most 👇 🧠 Core Concepts • Virtual DOM → Updates only what’s needed • Reconciliation → Efficient UI updates • Components → Reusable building blocks • Props vs State → Data flow ⚡ Hooks (Must Know) • useState → Manage state • useEffect → Handle side effects • useRef → Access DOM / persist values • useMemo & useCallback → Performance optimization 💡 Interview Tip: Don’t just write code. Explain it simply. Use analogies if needed. That’s what makes you stand out. 📌 Reality: Knowing React is good. Explaining React clearly is what gets you hired. 💬 Quick question: Which React concept do you find most confusing? #ReactJS #FrontendDevelopment #CodingInterviews #JavaScript #WebDevelopment

In one of my recent interviews, I was asked: Why do we add type: "module" in package.json? might seem like a simple question but it checks your fundamentals. By default, Node.js uses CommonJS (require statement) but if we want to use modern import and export, we add: "type": "module" This tells Node to treat our project as an ES Module. Without it, it gives a syntax error. #interview #react #node #nodejs #reactjs #job #js #interviewquestion

🚀 React Interview Series | Day 3: Why is State “Async”? You click a button, call: 👉 setCount(count + 1) 👉 then immediately: console.log(count) And boom… you still see the old value 😵 💡 The Real Talk: I’ve seen candidates panic in live coding rounds when this happens. They assume something is broken. It’s not. React is just being smart. Instead of updating state instantly, React batches updates to improve performance. 👉 Multiple state updates = ❌ multiple re-renders 👉 Batched updates = ✅ single efficient re-render 🧠 What’s Actually Happening? React waits until your function finishes execution, then processes all state updates together. That’s why you don’t see the updated value immediately. 🔥 The “Senior” Way to Handle It: If your next state depends on the previous one, never rely on the current variable. Use the functional update pattern 👇 setCount(prevCount => prevCount + 1); ✅ Always gets the latest value ✅ Works correctly even with multiple queued updates 🎯 Key Takeaway: If you understand this, you're already thinking like a senior developer. 💬 Have you ever been confused by this behavior in React? Drop your experience below 👇 #ReactJS #JavaScript #FrontendDevelopment #WebDevelopment #CodingInterview #ReactTips

⚛️ Still Confused About React Hooks? Most React interview questions revolve around just one thing: 👉 Hooks. But many developers only know useState and useEffect. Here’s a quick React Hooks Cheat Sheet you should actually know: 🔹 useState 🔹 useEffect 🔹 useContext 🔹 useRef 🔹 useMemo & useCallback 🔹 useReducer 🔹 useLayoutEffect 🔹 useTransition 🔹 useDeferredValue 🔹 useSyncExternalStore 🔹 Custom Hooks 🔹 Rules & Best Practices You don’t need to memorize everything. You need to understand: • When to use which hook • Why performance matters • How hooks work together 💬 Quick question: Which hook confused you the most when you first learned React? Save this for interview prep. #React #JavaScript #FrontendDevelopment #WebDevelopment #Coding

⚛️ Still Confused About React Hooks? Most React interview questions revolve around just one thing: 👉 Hooks. But many developers only know useState and useEffect. Here’s a quick React Hooks Cheat Sheet you should actually know: 🔹 useState 🔹 useEffect 🔹 useContext 🔹 useRef 🔹 useMemo & useCallback 🔹 useReducer 🔹 useLayoutEffect 🔹 useTransition 🔹 useDeferredValue 🔹 useSyncExternalStore 🔹 Custom Hooks 🔹 Rules & Best Practices You don’t need to memorize everything. You need to understand: • When to use which hook • Why performance matters • How hooks work together 💬 Quick question: Which hook confused you the most when you first learned React? Save this for interview prep. #React #JavaScript #FrontendDevelopment #WebDevelopment #Coding