Frontend Interview Questions: React, JavaScript and more

💼 Top 5 Frontend Interview Questions I Got Here are some questions I recently came across as a Frontend Developer 👇 1️⃣ What is the difference between == and === in JavaScript? 2️⃣ How does Angular change detection work? 3️⃣ What is trackBy in ngFor and why is it important? 4️⃣ Difference between Promises and Observables? 5️⃣ How do you improve performance in a frontend application? These questions made me realize how important fundamentals are 👀 Still learning and improving every day 🚀 What’s a question you’ve been asked in interviews? #FrontendDeveloper #Angular #JavaScript #InterviewPrep #WebDevelopment

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

🚀 Day 8 of Frontend Developer Interview Preparation Today I dived deeper into how JavaScript actually works behind the scenes ⚙️ 📌 Topics I learned: Event Loop Microtask Queue Callback Queue JavaScript Engine Understanding these concepts changed the way I look at async code. Now I know: 👉 JavaScript doesn’t “wait” — it manages everything using queues and the event loop 👉 Promises (microtasks) always execute before setTimeout (callback queue) 👉 The JS engine executes code using the call stack while Web APIs handle async tasks This is one of those topics that looks simple, but the deeper you go, the more interesting it becomes 🔥 Next step: I’ll practice tricky output-based questions on these concepts to strengthen my understanding 💪 If you’re preparing for frontend interviews, make sure you understand this topic well — it’s a game changer 🚀 #Day8 #FrontendDeveloper #JavaScript #EventLoop #WebDevelopment #InterviewPreparation

🚀 Day 9 of Frontend Developer Interview Preparation Today I explored some very important JavaScript concepts — setTimeout and Higher-Order Functions. ⏳ setTimeout Learned how JavaScript handles asynchronous behavior using the event loop. Even though we provide a delay, the execution depends on the call stack and callback queue — which makes it more interesting than it looks! 🔁 Higher-Order Functions (HOF) Understood how functions can take other functions as arguments or return them. This concept is widely used in JavaScript (like map, filter, reduce) and is possible because functions are treated as first-class citizens. 💡 Key Takeaways: JavaScript is single-threaded but handles async tasks efficiently setTimeout doesn’t guarantee exact timing — it depends on the execution flow Higher-Order Functions make code more reusable and powerful 📌 Consistency is the key — learning step by step and strengthening fundamentals. If you're also preparing for frontend interviews, feel free to connect or share your thoughts! #JavaScript #FrontendDevelopment #InterviewPreparation #100DaysOfCode #WebDevelopment #LearningInPublic

🚀 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

💡 Daily React/JavaScript Interview Tip When explaining concepts like closures, state, or hooks—don’t just define them. Show how they solve a real problem. 👉 Instead of saying: “A closure lets a function access variables from its outer scope.” ✅ Say: “Closures are useful when you want to preserve state without exposing it globally—for example, creating a private counter inside a function.” Interviewers are not just testing what you know—they’re evaluating how you think and apply knowledge in real scenarios. 📌 Tip: Always pair your explanation with a quick use case or example. It instantly makes your answer stronger and more memorable. #ReactJS #JavaScript #WebDevelopment #TechInterviews #FrontendDevelopment

❓ React Interview Question: What is useEffect? ✅ Answer: useEffect is a React Hook used to handle side effects in functional components. Side effects include operations like API calls, subscriptions, timers, and DOM updates. It runs after the component renders and can be controlled using a dependency array to decide when it should execute. 💡 Why we use useEffect? React components are meant to be pure, but real-world applications need to: --> fetch data from APIs --> set up event listeners --> work with timers useEffect allows us to perform these operations safely after rendering. #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #SoftwareEngineering #InterviewPreparation #CodingInterview

❓ 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

❓ React Interview Question: What are Controlled Components in React? 💡 In React, a Controlled Component is a component where the form data is handled by the React state , rather than the DOM itself. 👉 Follow Tarun Kumar for tech content, coding tips, and interview prep 🚀 #React #FrontendDevelopment #WebDevelopment #JavaScript #ReactJS #CodingInterview #SoftwareDevelopment

Mastering REACT.JS isn't about writing code it's about understanding the concepts that power modern web applications. We've put together a list of the 50 React.js interview questions. They cover: * The basics of React like JSX and Virtual DOM * State versus Props * topics, such as Hooks and Context API * Redux and performance optimization techniques * What to expect in a real-world interview This guide is for anyone who wants to learn React whether you're a student, a developer who wants to improve their skills or someone who is preparing for a job interview. It can help you feel more confident and clear, about React. Save this guide. Practice every day to stay ahead. Which React concept do you find difficult to understand? Lets talk about it! #ReactJS #WebDevelopment #Frontend #Coding #InterviewPrep #SoftwareEngineering #Developers #TechCareers #HNAYASKILLS #LearnToCode #PlacementPreparation