React forwardRef explained

🚀 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: 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

❓ React Interview Question: Difference between State and Props? 💡 What are Props? Props are inputs passed from parent to child components - They are read-only (immutable) - Used to make components reusable function Greeting(props) { return <h1>Hello {props.name}</h1>; } 💡 What is State? State is data managed inside a component - It can change over time (mutable) - Used for dynamic UI updates const [count, setCount] = useState(0); 💡 Key Differences props → Passed from parent, cannot be modified state → Managed inside component, can be updated props → Used for communication between components state → Used for handling dynamic data Follow Tarun Kumar for tech content, coding tips, and interview prep 🚀 #ReactJS #ReactInterview #FrontendInterview #JavaScript #CodingInterview #InterviewPrep #WebDevelopment #Developers #TechContent

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 Question: What does the dependency array of useEffect affect? 💡 In React, the dependency array in useEffect controls when the effect runs. 🔹 1. No Dependency Array useEffect(() => { console.log("Runs on every render"); }); - runs after every render 🔹 2. Empty Dependency Array [] useEffect(() => { console.log("Runs only once"); }, []); - runs only once (on component mount) 🔹 3. With Dependencies [value] useEffect(() => { console.log("Runs when value changes"); }, [value]); - runs only when the dependency changes - it prevents unnecessary re-renders - improves performance - helps control side effects (API calls, subscriptions, timers) 💡 How to remember useEffect dependency array? no dependency array → runs on every render empty array [] → runs only once (on mount) array with values [value] → runs only when the value changes 👉 Follow Tarun Kumar for tech content, coding tips, and interview prep 🚀 #ReactJS #JavaScript #FrontendDevelopment #ReactHooks #useEffect #CodingTips #WebDevelopment #SoftwareEngineering #InterviewPreparation #Developers

Most developers “learn React”… But still fail React interviews. Not because they don’t know React — But because they don’t know what actually gets asked. After analyzing multiple frontend interviews, here are Top 20 React Interview Questions you should master: Core Concepts 1. What is Virtual DOM & how does it work? 2. Difference between state vs props 3. What are hooks in React? 4. useState vs useReducer — when to use what? 5. What is useEffect & its lifecycle? Advanced Hooks & Patterns 6. How does useContext work internally? 7. How to avoid unnecessary re-renders? 8. What is memoization (React.memo, useMemo, useCallback)? 9. Controlled vs uncontrolled components 10. How to manage global state in React? Performance & Optimization 11. How React batching works? 12. What causes re-renders in React? 13. Code splitting & lazy loading 14. Key prop — why it is important? Architecture & Real-world 15. How to structure a scalable React project? 16. How do you handle API calls & caching? 17. How to implement a multi-step form? 18. How to share data between components (without prop drilling)? Interview Traps 19. Difference between useEffect vs useLayoutEffect 20. Why React is called declarative? 𝐠𝐞𝐭 𝐞𝐛𝐨𝐨𝐤 𝐰𝐢𝐭𝐡 (detailed 232 ques = 90+ frequently asked Javascript interview questions and answers, 70+ Reactjs Frequent Ques & Answers, 50+ Output based ques & ans, 23+ Coding Questions & ans, 2 Machine coding ques & ans) 𝐄𝐛𝐨𝐨𝐤 𝐋𝐢𝐧𝐤: https://lnkd.in/gJMmH-PF Follow on Instagram : https://lnkd.in/gXTrcaKP #javascript #javascriptdeveloper #reactjs #reactnative #vuejsdeveloper #angular #angulardeveloper

🚀 React Interview Question: What does Re-rendering mean in React? 💡Re-rendering in React means updating the UI when a component’s data changes. 🔹 Key Idea: When state or props change, React re-runs the component function and updates the UI to reflect the latest data. 🔹 Example: import React, { useState } from "react"; function Counter() { const [count, setCount] = useState(0); return ( <div> <p>Count: {count}</p> <button onClick={() => setCount(count + 1)}> Increment </button> </div> ); } Clicking the button updates the state --> React re-renders --> UI updates. 🔹 When does re-render happen? - state changes (useState) - props change - parent component re-renders 🔹 Note: React does NOT refresh the whole page — it efficiently updates only the changed parts using the Virtual DOM. Follow Tarun Kumar for more tech content and interview prep #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #CodingInterview #SoftwareEngineering #TechContent #DeveloperTips

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

🚀 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: useCallback vs useMemo in React When building React applications, unnecessary re-renders and expensive computations can impact performance. This is where hooks like useCallback and useMemo help optimize rendering efficiency. 🔹 useCallback Used to memoize a function, so it doesn’t get recreated on every render. This is especially useful when passing functions to child components to prevent unwanted re-renders. 🔹 useMemo Used to memoize a computed value, avoiding expensive recalculations unless dependencies change. 👉 Follow Tarun Kumar for tech content, coding tips, and interview prep 🚀 #ReactJS #ReactHooks #ReactInterviewQuestions #FrontendDevelopment #JavaScript #WebDevelopment #CodingInterview #SoftwareEngineering #TechTips #LearnToCode