React useEffect with empty dependency array explained

Most important question that was asked in React Developer interview Sharing the questions here in case it helps someone preparing for similar roles. Some of the questions they asked: 1. What is React and why is it efficient? 2. How does React work internally? 3. What is the most challenging task you handled in your project? 4. Is JavaScript tightly coupled or loosely coupled? 5. Why do we use TypeScript? 6. How does "extends" work in TypeScript and what is the difference between type and interface? 7. How does Redux work, from installation to usage in a project? 8. Have you used Redux Toolkit (RTK) or TanStack Query? 9. What is the difference between bind and apply in JavaScript? 10. What has been your experience with useCallback and useMemo in real projects? 11. What is the role of the dependency array in useEffect? Overall, the round was focused on practical understanding of React, TypeScript and JavaScript rather than just theory. 👨💻 Follow for daily React, and JavaScript #React #JavaScript #TypeScript #Redux #Frontend #InterviewExperience #capgemini

React Interview Series | Day 12 🚀 Q: How do you return multiple elements in React? https://lnkd.in/gqGJCyR7 ❌ Junior: Wrap everything in a <div> ✅ Senior: Use Fragments (<>...</>) Why it matters? • Avoid breaking Flexbox/Grid layouts • Reduce unnecessary DOM nodes • Improve performance & accessibility 💡 Pro Tip: Need a key? Use <React.Fragment key={id}> (not <>) 👉 Quick check: Got a <div> with no class/style? Replace it with a Fragment. Have you ever faced a layout break because of a mystery div? 😅👇 #ReactJS #CleanCode #Frontend #WebDevelopment #CodingInterview

I used to write React without knowing what was happening beneath the surface. Then I went down the rabbit hole of React internals. Fiber changed how I think about rendering, performance, and why React is designed the way it is. React Fiber is one of those things every React dev should understand but almost nobody does. Here's the full breakdown — reconciliation, scheduling, fiber nodes, double buffering — in 16 slides. If you're preparing for interviews or want to go beyond surface-level React… This is a must-know concept. Save this for later 🔖 #ReactJS #WebDevelopment #Frontend #JavaScript #ReactFiber #SoftwareEngineering #ProgrammingTips #LearnToCode #FrontendDevelopment #TechCarousel

One interesting question I recently came across in a React interview: 👉 “If JavaScript already has getElementById(), why do we need useRef in React?” Here’s the understanding 👇 ✅ React uses a Virtual DOM, so direct DOM manipulation is discouraged. ✅ useRef provides a safe way to access DOM elements inside React components. ✅ Updating a ref does not trigger re-render, making it useful for storing mutable values. ✅ It keeps code component-scoped, cleaner, and React-friendly. 📌 Simple Answer: useRef lets us access DOM elements and persist values across renders without affecting the component lifecycle. #reactjs #hooks #useref #frontend

𝐈 𝐀𝐬𝐤𝐞𝐝 𝐓𝐡𝐢𝐬 𝐐𝐮𝐞𝐬𝐭𝐢𝐨𝐧 𝐢𝐧 𝐚 𝐅𝐫𝐨𝐧𝐭𝐞𝐧𝐝 𝐈𝐧𝐭𝐞𝐫𝐯𝐢𝐞𝐰… 𝐚𝐧𝐝 𝐦𝐨𝐬𝐭 𝐝𝐞𝐯𝐞𝐥𝐨𝐩𝐞𝐫𝐬 𝐟𝐚𝐢𝐥𝐞𝐝 ❌ Question: When does a React component re-render? Example: function Counter() { const [count, setCount] = useState(0); console.log("Render"); return ( <button onClick={() => setCount(count + 1)}> {count} ); } What will happen when button is clicked? Answer 👇 Component will re-render every time state changes. In React, re-render happens when: ✔ State changes ✔ Props change ✔ Parent component re-renders Many developers think only state change causes re-render but parent re-render also triggers child render. Important Tip for Interview ⚠️ React re-render does NOT always mean DOM update. React compares Virtual DOM first, then updates UI. Good React developers know syntax. Great React developers know re-render logic. #ReactJS #FrontendDeveloper #JavaScript #WebDevelopment #ReactInterview #CodingInterview #NextJS #SoftwareDeveloper #UIDeveloper

𝐖𝐡𝐲 𝐃𝐨 𝐖𝐞 𝐔𝐬𝐞 𝐂𝐥𝐨𝐬𝐮𝐫𝐞𝐬 𝐢𝐧 𝐑𝐞𝐚𝐜𝐭 𝐉𝐒? 🤔 Closures are one of the most important concepts in JavaScript… and React uses them everywhere. But many developers don’t realize it 👇 What is a closure? A closure is when a function remembers the variables from its outer scope even after that scope has finished execution. How React uses closures 👇 🔹 Event Handlers Functions like onClick capture state values at the time they are created 🔹 Hooks (useState, useEffect) Hooks rely on closures to access state and props inside functions 🔹 Async operations (setTimeout, API calls) Closures hold the state values when the async function was created Example 👇 const [count, setCount] = useState(0); const handleClick = () => { setTimeout(() => { console.log(count); }, 1000); }; What will this log? 🤔 It logs the value of count at the time handleClick was created This is why we sometimes face “stale closure” issues ⚠️ Why this matters? Understanding closures helps you: ✔ Debug tricky bugs ✔ Avoid stale state issues ✔ Write better React logic Tip for Interview ⚠️ Don’t just define closures Explain how they behave in React That’s what interviewers look for Good developers use React. Great developers understand how it works under the hood. 🚀 #ReactJS #JavaScript #Closures #FrontendDeveloper #WebDevelopment #ReactInterview #CodingInterview #SoftwareDeveloper

🚀 Day 6 – Frontend Interview Series 🔥 Topic: Promises (Async JavaScript) 💡 What is a Promise? A Promise in JavaScript is an object that represents the result of an asynchronous operation (like API calls, timers, file reading). 👉 It has 3 states: Pending ⏳ Resolved (Fulfilled) ✅ Rejected ❌ 📦 Basic Example const myPromise = new Promise((resolve, reject) => { let success = true; if (success) { resolve("Task completed!"); } else { reject("Task failed!"); } }); myPromise .then((res) => console.log(res)) .catch((err) => console.log(err)); ⚡ Why Promises? 👉 To avoid callback hell 👉 To handle async code in a clean way 👉 Better readability & chaining #JavaScript #ReactJS #FrontendDeveloper #InterviewPrep #AsyncJS

🚀 React Interview Series – Day 13 Today’s topic: JSX, Babel & Webpack (Explained Simply) 💡 If you're starting with React, these 3 terms can feel confusing — but they’re actually easy 👇 👉 1. JSX (JavaScript XML) JSX lets you write HTML inside JavaScript. It makes UI code cleaner and easier to understand. Example: Instead of writing complex JS → you write: <h1>Hello World</h1> 👉 2. Babel Browsers don’t understand JSX directly. Babel converts JSX into normal JavaScript that browsers can run. 👉 3. Webpack Webpack bundles all your files (JS, CSS, images) into one optimized file. It makes your app fast and production-ready. ⚡ Simple Flow: JSX → (Babel converts) → JS → (Webpack bundles) → Browser 🎯 Interview Tip: If asked: “Can browsers understand JSX?” Answer: ❌ No — it must be converted using Babel. 💬 Follow for daily React interview prep #reactjs #javascript #frontenddeveloper #webdevelopment #codinginterview #learnreact #100daysofcode #programming #reactinterview #react

Recently attended an interesting frontend interview for a product-based project. Sharing some of the questions/topics discussed — might help others preparing 👇 🔹 React & Performance - How do you optimize React bundle size? (code splitting, lazy loading, tree shaking) - What are techniques to improve initial load time? 🔹 React Query - How does caching work in React Query? - Difference between stale time vs cache time - How would you handle refetching and background updates? 🔹 JavaScript Concepts - What is debouncing? Where have you used it in real projects? - Difference between debouncing and throttling 🔹 Redux - How do you handle error states in Redux? - Best practices for managing API errors globally 🔹 Accessibility (Important 🔥) - How do you build a website for specially-abled users? - What are ARIA roles and when do you use them? - How do you ensure keyboard navigation and screen reader support? 🔹 Scenario-Based - How would you design API error handling across the application? - What approach would you take to improve performance of a slow UI? 💡 Key takeaway: Interviews are focusing heavily on real-world scenarios, performance, and accessibility — not just theory. #frontend #reactjs #javascript #webdevelopment #interviewpreparation #redux #reactquery #accessibility

“How does React re-render components?” Here’s how I explain it in interviews 👇 When state or props change: → React re-executes the component function → Creates a new virtual DOM → Compares with previous version → Updates only what changed Important part: Re-render ≠ DOM update Problem in real apps: → Too many unnecessary re-renders → Caused by poor state placement How I handle it: ✔ Keep state close to usage ✔ Avoid unnecessary prop changes ✔ Structure components properly Key insight: Understanding re-renders is key to React performance. #ReactJS #Frontend #Performance #JavaScript #SoftwareEngineering #InterviewPrep #Engineering #WebDevelopment #Tech