useEffect Hook in React for Side Effects

I’m starting a series of React interview questions, structured from fundamentals to advanced concepts. (Part 1) focuses on the basics: 1. What is JSX? 2. What is React? 3. What are components in React? 4. What is the Virtual DOM? 5. What are props in React? 6. What is the DOM? 7. What is state in React? 8. What is the difference between State and Props? 9. What are fragments in React? 10. What are the key features of React? More parts coming soon covering intermediate and advanced topics. #ReactJS #FrontendDevelopment #InterviewPreparation #SoftwareEngineering

❓ 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

Day 9 – React Interview Journey 🚀 DOM: The Document Object Model is a tree structure of your webpage that browsers use to display and update content. Why Virtual DOM? The Virtual DOM was created to improve performance by minimizing direct updates to the real DOM. 💬 What’s one React concept you struggled with at first? Drop it below 👇 #Day9 #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #CodingJourney #InterviewPrep

💡 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

⚛️ Top React Interview Questions Every Developer Should Prepare React is one of the most widely used libraries for building modern user interfaces. If you're preparing for a frontend or React developer interview, mastering the core concepts is essential. Here are some important React interview topics you should know: ✔ What is React and why is it used? ✔ Virtual DOM and how React updates the UI ✔ Functional Components vs Class Components ✔ React Hooks (useState, useEffect, useMemo, useCallback) ✔ Props vs State ✔ React Lifecycle Methods ✔ Controlled vs Uncontrolled Components ✔ Context API and when to use it ✔ React Performance Optimization ✔ Code Splitting and Lazy Loading ✔ Error Boundaries ✔ Custom Hooks ✔ Server-Side Rendering (SSR) --- Preparing these concepts will help you crack React interviews at product-based and service-based companies. Focus on core concepts, performance optimization, and real-world use cases. #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #ReactInterview #Programming #SoftwareDevelopment #CodingInterview #Developers #TechInterview #ReactDeveloper

Top 10 React Hooks Interview Questions 1. What are the benefits of using Hooks in React? 2. What are the rules of React Hooks? 3. What is the difference between useEffect and useLayoutEffect in React? 4. What does the dependency array of useEffect affect? 5. What is the useRef hook and when should you use it? 6. What is useCallback? 7. What is the useMemo hook in React and when should it be used? 8. What is the useReducer hook in React and when should it be used? 9. What is the useId hook in React and when should it be used? 10. How to create and use Custom Hooks in React? Connect/Follow Tarun Kumar for more tech content and interview prep #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #ReactHooks #CodingInterview

🚀 Day 962 of #1000DaysOfCode ✨ 5 Most Important Questions on Virtual DOM Virtual DOM is one of the most talked-about concepts in React — yet many developers only understand it on the surface. In today’s post, I’ve covered 5 of the most important questions around the Virtual DOM that are commonly asked in interviews and real-world discussions. From how it actually works to why it improves performance, these questions will help you build a deeper and clearer understanding of what’s happening behind the scenes. This is not just theory — it’s about knowing how React optimizes updates and why your UI feels fast and efficient. If you’re working with React or preparing for interviews, mastering these questions can give you a strong edge. 👇 Which Virtual DOM question has confused you the most so far? #Day962 #learningoftheday #1000daysofcodingchallenge #FrontendDevelopment #WebDevelopment #JavaScript #React #CodingCommunity #ReactJS

❓ 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

Day 8 of my React Interview Journey  Today’s topic: Difference between Redux and Context API State management is one of the most important concepts in React applications. Both Redux and Context API help us manage state, but they solve different problems: Redux Centralized state management Best for large-scale applications Powerful but comes with setup complexity Context API Built-in React feature Best for small to medium apps Simple and lightweight for sharing state 👉 What do you think: When should we prefer Redux over Context API? 💬 Drop your thoughts in the comments below! #ReactJS #Redux #ContextAPI #WebDevelopment #JavaScript #FrontendDevelopment #CodingJourney #100DaysOfCode #MERNStack #InterviewPreparation

🚀 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