React useCallback vs useMemo: Performance Optimization

[Day 3/100] Daily Interview Questions for React JS Developers ⚛️ The Scene: The technical interview. The interviewer leans in and asks a deceptively simple question: "Can you list the React Hooks for me?" 🚩 The Rookie Mistake: Rattling off a random, disorganized list of hooks as they pop into your head. ✅ The Senior Approach: Grouping them logically to show the interviewer your brain is organized and you understand frontend architecture. Here is the framework that wins the interview: 🔥 1. The "Big Three" (Your Daily Drivers): useState: Manages local component state. useEffect: Handles side effects (fetching data, subscriptions, manual DOM changes). useContext: Consumes global state cleanly without prop drilling. ⚡ 2. The Performance Hooks (Crucial for Tier 1 Interviews): useMemo: Caches a calculated value. useCallback: Caches a function definition. 🛠️ 3. The Ref & State Management Hooks: useRef: Holds a mutable value that does NOT trigger a re-render when updated (often used to access DOM elements directly). useReducer: An alternative to useState for complex state logic, working similarly to Redux (state + action). (Pro Tip: There are others like useLayoutEffect or useId, but clearly explaining these core 7 proves you have the tools required for an enterprise app.) 👨💻 Looking for a React developer who understands the "why" behind the code? I am currently taking on new Freelance Projects! Whether you need scalable frontend architecture, complex state management, or a full custom web app build, I bring clean code and strategic thinking to the table. 📩 DM me to discuss bringing your next project to life! contact me: https://lnkd.in/g3Pe55iZ Hit Follow for Day 4 tomorrow! How do you usually explain useReducer to junior devs? Let's discuss below! 👇 #ReactJS #FrontendDeveloper #WebDevelopment #SoftwareEngineering #CodingInterview #JavaScript #ReactHooks #FreelanceDeveloper #100DaysOfCode #TechCommunity

Recently, I interviewed for multiple Senior React.js & Tech Lead roles — and noticed a pattern. Most interviewers asked basic but frequently repeated questions that test your clarity of concepts + coding approach. Here are the Top 10 common questions I was asked 👇 1️⃣ Call, Apply, Bind → Difference + Polyfill implementation 2️⃣ Flatten an Array without Array.flat() 👉 Input: [1,2,3,[4,5,6,[7,8,[10,11]]],9] 👉 Output: [1,2,3,4,5,6,7,8,10,11,9] 3️⃣ Inline 5 divs in a row without flex/margin/padding (Hint: display: inline-block) 4️⃣ Find sum of numbers without a for loop (Hint: reduce() / recursion) 5️⃣ Deep Copy vs Shallow Copy — behavior & how to achieve it 6️⃣ Promise & Async/Await output puzzle 7️⃣ Find first repeating character (e.g., "success" → "c") 8️⃣ Stopwatch Implementation (Start, Stop, Reset + live timer) 9️⃣ Build a To-Do List (Vanilla JS/React) → optimize re-renders 🔟 Currying for Infinite Sum 👉 sum(10)(20)(30)() → 60 👉 sum(10)(20)(30)(40)(50)(60)() → 210 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

Frontend interviews are no longer just about React. They’re about how deeply you understand JavaScript and the web. Here’s what modern frontend interviews actually cover 👇 🔹 JavaScript Core & Advanced • First-class functions • Execution context & call stack • Hoisting & Temporal Dead Zone (TDZ) • this (regular vs arrow functions) • Currying & pure vs impure functions • Debounce vs throttle • Shallow vs deep copy • undefined vs null, optional chaining, nullish coalescing • Garbage collection & memory management • Event loop, streams & backpressure • Performance pitfalls (e.g. object de-optimization) 🔹 Async & Architecture • Promises & async/await flow • Concurrency handling • Preventing starvation • Task scheduling & execution order 🔹 React & Frontend Fundamentals • JSX & reconciliation • Component lifecycle (actual phases) • Controlled vs uncontrolled components • Error boundaries • Event handling patterns • useEffect behavior & optimization 🔹 Next.js & Backend Awareness • Server-side handling • API methods (GET, POST, PUT, DELETE) • REST structure & optimization thinking 🔹 Problem Solving • Breaking problems step-by-step • Optimization thinking before coding • Handling edge cases 💡 The shift is clear: Frontend interviews are moving from “Can you build UI?” → “Do you understand systems?” If you’re preparing, don’t just focus on frameworks. Focus on how things work under the hood. Which area do you think is the hardest — JavaScript, React, or System Design? 👇 #Frontend #JavaScript #React #NextJS #CodingInterview #SoftwareEngineering

Frontend interviews are no longer just about React. They’re about how deeply you understand JavaScript and the web. Here’s what modern frontend interviews actually cover 👇 🔹 JavaScript Core & Advanced • First-class functions • Execution context & call stack • Hoisting & Temporal Dead Zone (TDZ) • this (regular vs arrow functions) • Currying & pure vs impure functions • Debounce vs throttle • Shallow vs deep copy • undefined vs null, optional chaining, nullish coalescing • Garbage collection & memory management • Event loop, streams & backpressure • Performance pitfalls (e.g. object de-optimization) 🔹 Async & Architecture • Promises & async/await flow • Concurrency handling • Preventing starvation • Task scheduling & execution order 🔹 React & Frontend Fundamentals • JSX & reconciliation • Component lifecycle (actual phases) • Controlled vs uncontrolled components • Error boundaries • Event handling patterns • useEffect behavior & optimization 🔹 Next.js & Backend Awareness • Server-side handling • API methods (GET, POST, PUT, DELETE) • REST structure & optimization thinking 🔹 Problem Solving • Breaking problems step-by-step • Optimization thinking before coding • Handling edge cases 💡 The shift is clear: Frontend interviews are moving from “Can you build UI?” → “Do you understand systems?” If you’re preparing, don’t just focus on frameworks. Focus on how things work under the hood. Which area do you think is the hardest — JavaScript, React, or System Design? 👇 #Frontend #JavaScript #React #NextJS #CodingInterview #SoftwareEngineering

𝗧𝗼𝗽 𝗥𝗲𝗮𝗰𝘁 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄 𝗤𝘂𝗲𝘀𝘁𝗶𝗼𝗻𝘀 | 𝗥𝗲𝗮𝗰𝘁.𝗷𝘀 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄 𝗣𝗿𝗲𝗽𝗮𝗿𝗮𝘁𝗶𝗼𝗻 𝗳𝗼𝗿 𝗗𝗲𝘃𝗲𝗹𝗼𝗽𝗲𝗿𝘀 Preparing for a React.js interview? In this video, we cover the most commonly asked React interview questions that every Frontend and React Developer should know. React is one of the most popular JavaScript libraries for building modern user interfaces, and understanding its core concepts is essential for cracking frontend developer interviews. In this guide, you will revise important React fundamentals, hooks, performance optimization techniques, and best practices that are frequently asked in technical interviews. Topics Covered: What is React and how it works Virtual DOM and Reconciliation Components and Props State and Lifecycle methods React Hooks (useState, useEffect, useRef) useEffect vs useLayoutEffect Controlled vs Uncontrolled Components Context API vs Redux React Performance Optimization Lazy Loading and Code Splitting This video is useful for Frontend Developers, React Developers, and Full Stack Developers preparing for technical interviews in product-based and service-based companies. hashtag #ReactJS hashtag #ReactInterviewQuestions hashtag #FrontendDeveloper hashtag #JavaScript hashtag #ReactDeveloper hashtag #WebDevelopment hashtag #CodingInterview hashtag #TechInterview hashtag #SoftwareDeveloper hashtag #ReactHooks hashtag #FrontendEngineering hashtag #InterviewPreparation hashtag #WebDeveloper

𝟮𝟯 𝗔𝗱𝘃𝗮𝗻𝗰𝗲𝗱 𝗥𝗲𝗮𝗰𝘁 𝗦𝗰𝗲𝗻𝗮𝗿𝗶𝗼-𝗕𝗮𝘀𝗲𝗱 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄 𝗤𝘂𝗲𝘀𝘁𝗶𝗼𝗻𝘀 | 𝗥𝗲𝗮𝗰𝘁𝗝𝗦 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄 𝗣𝗿𝗲𝗽𝗮𝗿𝗮𝘁𝗶𝗼𝗻 In this video, we cover 23 advanced React scenario-based interview questions that are frequently asked in product-based companies and senior frontend interviews. Scenario-based questions test your real-world problem-solving ability, not just theory. These questions focus on performance optimization, state management, rendering behavior, and architecture decisions in React applications. In this video you will learn: Handling unnecessary re-renders in React Optimizing performance using React.memo, useMemo, and useCallback Managing large lists and data efficiently Handling API calls and race conditions Designing scalable React component architecture Using custom hooks for reusable logic Handling state management with Context API / Redux Improving React app performance Handling form performance and validation Debugging React rendering issues These questions are very helpful for developers preparing for React Developer interviews with 2–5 years of experience. Perfect for Frontend Developers, Full Stack Developers, and React Engineers preparing for technical interviews. #ReactJS #ReactInterviewQuestions #FrontendDeveloper #JavaScript #ReactDeveloper #WebDevelopment #CodingInterview #Programming

🚀 Day 20/100 – Implementing a curry() Function in JavaScript Today I explored an advanced JavaScript concept: Currying. Currying transforms a function with multiple arguments into a sequence of functions, each taking a single argument. 🧠 Problem: Convert a function so that it can be called like: sum(1)(2)(3) // 6 ✅ Solution: function curry(fn) { return function curried(...args) { if (args.length >= fn.length) { return fn(...args); } else { return function (...nextArgs) { return curried(...args, ...nextArgs); }; } }; } function sum(a, b, c) { return a + b + c; } const curriedSum = curry(sum); console.log(curriedSum(1)(2)(3)); console.log(curriedSum(1, 2)(3)); console.log(curriedSum(1)(2, 3)); ✅ Output: 6 6 6 💡 Key Learnings: • Currying allows partial application of functions • Helps create reusable and flexible functions • Improves function composition • Common in functional programming 📌 Real World Usage: • Used in utility libraries like Lodash • Helps in writing cleaner React code • Useful in event handling and reusable logic Understanding currying improves how you think about functions and composition in JavaScript. I’m currently open to Frontend Developer opportunities (React / Next.js) and available for immediate joining. 📩 Email: bantykumar13365@gmail.com 📱 Mobile: 7417401815 If you're hiring or know someone who is, I’d love to connect. #OpenToWork #FrontendDeveloper #JavaScript #ReactJS #NextJS #ImmediateJoiner #100DaysOfCode

Frontend is not about how many frameworks you know. It’s not a race between Angular vs React vs Vue. And it’s definitely not about adding one more library to your resume every month. Frontend is about understanding the why behind what you build. Can you: • Structure a UI so it scales? • Manage state without creating chaos? • Write code that another developer can actually read? • Think about performance before users complain? • Build something that feels simple to the user… even if it’s complex underneath? Frameworks will change. Trends will shift. But fundamentals? They stay. I’ve seen developers jump from one framework to another… but still struggle with the same problems. Because the real skill isn’t “knowing a framework” — it’s knowing how the web works. So instead of asking: 👉 “Which framework should I learn next?” Start asking: 👉 “Am I actually getting better at frontend?” #FrontendDevelopment #WebDevelopment #SoftwareEngineering #Angular #React #Learning #CareerGrowth

I recently attended an interview for a Senior React JS Developer role at a product-based company (Copart), TR-2. it turned out to be more than just an interview — it was a strong learning experience. What made it impactful was the focus on real-world problem solving — not just “what you know,” but how you apply it under real scenarios. Here are some real-world scenario-based questions that really made me think: 🔹 JavaScript ->In a live application where users report slowness, how would you identify whether the issue is due to the event loop blocking or inefficient code? ->You have a feature using closures, but it's causing unexpected behavior in production — how would you debug and fix it? ->A page is consuming too much memory over time — how would you detect and prevent memory leaks? ->How would you handle multiple API calls efficiently without blocking the UI? 🔹 React JS ->In a large-scale application, components are re-rendering unnecessarily — how would you identify and fix performance issues? ->You are building a real-time dashboard — how would you manage frequent state updates without affecting performance? ->How would you design component structure for scalability in a production-level app? ->A user complains about slow UI after data load — how would you optimize rendering and improve UX? 🔹 Redux -> In a complex application, state is becoming hard to manage — how would you restructure your Redux store? ->How would you handle multiple dependent API calls using Redux Thunk or Saga in a real-world scenario? ->If Redux is causing too many re-renders, how would you optimize it? ->When would you decide NOT to use Redux and choose a simpler solution? This experience reminded me of something important: 👉 Interviews are not just about getting selected — they are about discovering how much you can grow. 👉 Real-world thinking is the real skill that sets you apart. Grateful for the opportunity, the challenges, and the learning that comes with stepping out of the comfort zone. On to the next challenge 🚀 #JavaScript #ReactJS #Redux #InterviewExperience #FrontendDevelopment #CareerGrowth #KeepLearning

Being an Experienced frontend developer, do you really think your HTML in depth knowledge is good? Check out what I got recently Was in an interview recently. The interviewer asked me about HTML <meta> tags — viewport, charset, description, robots. Standard stuff. I was in the zone. Then came the curveball: “What happens if you remove <!DOCTYPE html> from your HTML file?” I paused for a second. I knew something bad happened, but I had never articulated it clearly. Here’s what actually happens The browser switches to Quirks Mode — it starts rendering your page using Internet Explorer 5-era rules instead of modern standards. Your CSS box model breaks. Media queries become unpredictable. Layouts go haywire. And document.compatMode would reveal "BackCompat" instead of "CSS1Compat". That single line <!DOCTYPE html> is the reason your beautifully crafted CSS doesn’t fall apart across browsers. It’s not optional. It’s a contract with the browser. This moment reminded me how much of HTML we take for granted as React developers. We’re so deep in JSX, hooks, and state management that we sometimes forget the foundation our components sit on. So I made a cheat sheet not the basic stuff you Google every day, but the bits that actually matter in interviews and real-world debugging: 1. Meta tags (including Open Graph + Twitter Cards) 2. DOCTYPE + Quirks Mode explained 3. emantic HTML5 elements 4. Accessibility attributes (ARIA, tabindex, role) 5. Performance hints (preload, prefetch, defer vs async) 6. Security attributes (SRI integrity, sandbox, crossorigin) 7. Hidden gems: <dialog>, <template>, <details> without JS 8. Data attributes + Link rel values Save this. It’ll come up when you least expect it. What’s the most unexpected HTML question you’ve been asked in an interview? Drop it below 👇 #HTML5 #Frontend #WebDevelopment #LearningInPublic #ReactDeveloper #InterviewPrep #JavaScript #FrontendEngineering