Redux Toolkit vs Core Redux for React Applications

React Interview Question: What happens when setState is called? 💡 setState is used to update the state of a component but it doesn’t update immediately. 🔹 What actually happens when setState is called: - react schedules the state update (it doesn’t update instantly) - multiple setState calls may be batched for performance - react triggers the reconciliation process (Virtual DOM diffing) - only the changed parts of the UI are updated in the real DOM 🔹Key points to keep in mind: - setState is asynchronous (in most cases) - It may batch multiple updates together - It triggers a re-render of the component - react updates only what’s necessary (efficient DOM updates) 🔹State Update Patterns in React This pattern belongs to class components, not hooks setState({ count: count + 1 }); --> //Invalid in hooks In hooks, use the state setter function setCount(count + 1);  //basic update setCount(prev => prev + 1); // functional update (recommended for safety) In class components: this.setState({ count: this.state.count + 1 }); //direct update this.setState(prev => ({ count: prev.count + 1 })); // functional update (preferred) Connect/Follow Tarun Kumar for more tech content and interview prep #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #InterviewPrep

🚀 ReactJS Interview Breakdown — Topic-Wise Questions You MUST Prepare 👇 Just completed a strong technical round, and here’s a structured breakdown of questions asked topic-wise 👇 --- 🧠 JavaScript (Core Concepts) - What is the Event Loop? How does async execution work? - Output-based questions: - "10 > 9 > 8" → why? - Array ".push()" return value behavior - Type coercion and comparison logic --- ⚛️ ReactJS - How does rendering work in React? - What is the role of "useEffect"? (dependency array, cleanup) - Difference between "useMemo" and "useCallback" - When do unnecessary re-renders happen? --- 🧭 React Router - Difference between "useNavigate" and "useLocation" - When to use each in real scenarios --- 🔄 State Management (Redux) - Redux vs Redux Toolkit - What is Store vs State? - What does store actually contain? --- 🌐 API Handling - What are Axios Interceptors? - Where have you used them in real projects? - Handling auth tokens & global error handling --- 💻 Coding Questions - Find starting index of substring (case-sensitive & insensitive) - Find ALL occurrences of a word - Handle edge cases (ignore punctuation like ".", "!") - Group array of objects → "{ age: [names] }" - Write polyfill for "Array.prototype.filter" - Merge two arrays and sort (without inbuilt methods) --- 🔥 What they really evaluate - Problem-solving approach - Edge case handling - Clean and optimized code - Real-world experience over theory --- 💡 If you’re preparing for React interviews: 👉 Focus on concept clarity + coding + real use cases --- Drop a 🔥 if you want: - Answers to these questions - Machine coding patterns - Last-minute revision sheet #ReactJS #JavaScript #FrontendInterview #Redux #CodingInterview #WebDevelopment

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 13 of My Frontend Developer Interview Preparation Today I focused on understanding the “this” keyword in JavaScript along with revising some core basics. 🔹 Learned how this behaves differently based on context: In global scope Inside objects Inside regular functions vs arrow functions In event handlers 🔹 Understood that this is not fixed — it depends on how a function is called, which makes it a very important (and sometimes tricky) concept in interviews. 🔹 Also revised key JavaScript fundamentals: Arrays & Objects Shallow vs Deep Copy Destructuring Spread & Rest Operators 💡 The more I learn, the more I realize that strong fundamentals are the real game changer for cracking interviews. Tomorrow’s plan: Practice tricky questions on these topics and strengthen my problem-solving 🚀 #JavaScript #FrontendDevelopment #WebDevelopment #CodingJourney #InterviewPreparation #LearningEveryday

🚀 React Interview Series | Day 13: What are Hooks in React? The Interview Question: Video Explanation: https://lnkd.in/dfUs4JpB 👉 “What are Hooks in React?” 💡 Simple Answer: Hooks are special functions that allow you to 'hook into' React’s internal state and lifecycle features from functional components. 🧠 Before Hooks: We used class components More complex code 😵💫 🔥 After Hooks: Everything in functional components Cleaner & easier to manage ✅ 📦 Most Common Hooks: 👉 useState → to store and update data 👉 useEffect → to run logic when something happens ⚡ When to use Hooks? When you need to store user input or dynamic data When you need to call an API When something should happen on load/update When building interactive UI 🎯 Why use Hooks? Cleaner and shorter code ✅ No need for class components Easy to reuse logic (custom hooks) Makes code more readable & maintainable ⚡ Example: const [count, setCount] = useState(0); useEffect(() => { console.log("Component loaded"); }, []); 🔥 Pro Tip: Don’t just memorize hooks — understand when and why to use them in real projects 💬 Tomorrow Question: What is jsx, babel, webpack #reactjs #frontenddevelopment #javascript #webdevelopment #reacthooks #codinginterview #learnreact

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

🚀 React Interview Series – Day 15 🎯 What is a Reducer in Redux? (Beginner Friendly) If you're learning Redux, you’ll hear the term reducer a lot. Let’s break it down in the simplest way 👇 👉 A reducer is just a pure function that decides how your state should change based on an action. 📦 Think of it like this: You have a box (state) and you send an instruction (action) → the reducer updates the box accordingly. 💡 Basic Syntax: const reducer = (state, action) => { switch(action.type) { case "INCREMENT": return { count: state.count + 1 }; case "DECREMENT": return { count: state.count - 1 }; default: return state; } }; 🧠 Key Points to Remember: ✔️ Reducers are pure functions (no API calls, no side effects) ✔️ They always return a new state (don’t modify the old one) ✔️ They depend only on state + action 🔥 Real-Life Example: Counter App Action: “Increase count” Reducer: Adds +1 to current state Result: Updated count ⚡ In Simple Words: Reducer = "If this action happens → update state like this" 💬 Interview Tip: If asked “What is a reducer?” say: 👉 A reducer is a pure function in Redux that takes the current state and an action, and returns a new updated state based on the action type. 📌 Follow for more React Interview Questions #ReactJS #Redux #JavaScript #WebDevelopment #Frontend #InterviewPrep #LearnCoding

🚀 React Interview Question Breakdown – Can You Spot the Issues? Recently, I came across some interesting React interview questions focused on debugging and code optimization. Sharing them here 👇 🔍 Question 1: Find the issues and fix them const items = useSelector(state => state.items); const [filtered, setFiltered] = useState(items); useEffect(() => { setFiltered(items.filter(i => i.name.includes(search))); }, []); 🔍 Question 2: Find the issues and fix them const handleLike = async () => { const newCount = likes + 1; setLikes(newCount); await api.updateLikes(newCount); if (condition) { setLikes(likes + 1); // Review point } }; #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #InterviewQuestions #ReactHooks

🚀 React Interview Question : What is the useReducer hook and when should you use it? 💡 useReducer is a React hook that lets you manage state using a centralized function (reducer) that handles all state updates based on actions. 🔹 Basic Syntax const [state, dispatch] = useReducer(reducer, initialState); state → current state dispatch → function to send actions reducer → function that decides how state changes 🔹 How it works const reducer = (state, action) => { switch (action.type) { case "INCREMENT": return { count: state.count + 1 }; case "DECREMENT": return { count: state.count - 1 }; default: return state; } }; dispatch({ type: "INCREMENT" }); 🔹 Why use useReducer? - helps manage complex state logic - keeps state updates organized and predictable - avoids messy multiple useState calls 🔹 When should you use it? - state has multiple related values - logic involves multiple conditions (switch/if) - state updates depend on previous state - for better structure & scalability 🔹 Example Use Cases - form handling with many fields - complex UI state (toggles, filters, steps) - managing state transitions (like loading → success → error) Follow Tarun Kumar for tech content, coding tips, and interview prep #ReactJS #JavaScript #WebDevelopment #FrontendDeveloper #Coding #Programming #Developers #SoftwareEngineer #Tech

🚀 React Interview Question: How do you optimize React Context to reduce unnecessary re-renders? 💡 React Context is a common way to share data across components But if it’s not handled carefully, it can lead to extra re-renders, whenever the context value changes, all the components using it re-render. 🔹 1. Split your Context Don’t put everything in one place - keep contexts small and focused for better performance 🔹 2. Memoize the value Context updates are based on reference changes. - use useMemo to keep the value stable 🔹 3. Avoid inline functions New function creates a new reference, which causes a re-render - use useCallback 🔹 4. Use selector pattern Don’t consume the entire context if you only need one value 🔹 5. Keep state local when possible Not everything needs to live in Context 🔹 6. Use React.memo Helps prevent unnecessary child re-renders 🔹 Key Insight: React Context doesn’t check deep changes It only checks if the reference has changed So to optimize: - keep values stable - split contexts smartly - avoid unnecessary updates Connect/Follow Tarun Kumar for more tech content and interview prep #React #FrontendDevelopment #JavaScript #WebDev #SoftwareEngineering #CodingInterview