React Interview Series Day 13: JSX Babel Webpack Explained

Being strong in JavaScript and TypeScript is the gateway to crack interviews. Not just surface level. Get into depth. Look into how it actually works. Trust me, it gets interesting day by day. One such concept which I loved and still love to explain and solve: Event Loop Most developers know the definition. Few actually feel how it works. Let me break it down: JavaScript is single-threaded. One call stack. One thing at a time. So how does it handle setTimeout, API calls, and UI updates — all without freezing? That's where the Event Loop steps in. Here's what's actually happening under the hood: 🔹 Call Stack — Where your code executes. Functions get pushed in, popped out. 🔹 Web APIs — setTimeout, fetch, DOM events? These are handed off to the browser. JS doesn't wait. 🔹 Callback Queue (Macrotask Queue) — Once a Web API finishes, its callback waits here. 🔹 Microtask Queue — Promises land here. Higher priority than the callback queue. 🔹 Event Loop — Constantly watching. The moment the call stack is empty, it picks from the microtask queue first, then the callback queue. A classic interview question that trips people up: console.log("1"); setTimeout(() => console.log("2"), 0); Promise.resolve().then(() => console.log("3")); console.log("4"); The Output: 1 → 4 → 3 → 2 Why? Because setTimeout goes to the callback queue, but the Promise microtask jumps ahead in priority — even with a 0ms delay. This is the kind of depth that separates a developer who uses JavaScript from one who understands it. What's your favorite JS concept that changed how you think about code? Drop it in the comments! #JavaScript #TypeScript #EventLoop #WebDevelopment #InterviewPrep #FrontendDevelopment #JSDeepDive #LearningEveryDay

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

🚀 JavaScript Event Loop Explained (Must-Know Concept) Understanding the Event Loop is a game changer when it comes to writing efficient and predictable asynchronous JavaScript code. We use setTimeout, Promises, and async/await every day — but do we really know what’s happening behind the scenes? 🤔 Let’s break it down 👇 🔹 How the Event Loop Works: • JavaScript runs on a single thread • Synchronous code executes first (Call Stack) • Then Microtasks run (e.g., Promises, queueMicrotask) • Next, one Macrotask executes (e.g., setTimeout, events) • This cycle keeps repeating continuously ⚡ Execution Priority: 1️⃣ Synchronous Code 2️⃣ Microtasks 3️⃣ Macrotasks 💡 Why this matters: ✅ Helps debug async issues easily ✅ Avoids unexpected execution order ✅ Builds more predictable React apps ✅ Frequently asked in frontend interviews 📌 Pro Tip: Always remember — Promises (microtasks) run before setTimeout (macrotasks), even with 0ms delay! 💬 Are you confident with the Event Loop? Drop your thoughts below! #JavaScript #EventLoop #FrontendDevelopment #ReactJS #WebDevelopment #AsyncJavaScript #InterviewPrep #SoftwareEngineering

🚀 Stop Googling React syntax again and again… What if you had everything in one place? 👇 I created a React.js Cheat Sheet to help you build faster and code smarter 📚 What’s inside: • JSX fundamentals • Core concepts of React.js • Essential Hooks (useState, useEffect & more) 💡 Who is this for? ✔ Beginners starting with React ✔ Developers preparing for interviews ✔ Engineers who want faster development & cleaner code 📌 Pro Tip: Great developers don’t memorize everything… They create systems & references they can rely on. 💾 Save this post so you don’t have to search again while building 💬 Let’s discuss: What was the most confusing React concept for you when you started? Follow M. WASEEM ♾️ for more valuable content #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #ReactHooks #CodingLife #DevTips

Great developers don’t try to remember everything. They build systems that remember for them. A cheat sheet isn’t a shortcut— it’s a smart way to move faster.

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

What is a Component? A reusable building block of a user interface. 🔹 Functional Components ⚡ ✔ Simple & easy to write ✔ Use Hooks (useState, useEffect) ✔ Preferred in modern React 🔹 Class Components 🏗 ✔ Uses lifecycle methods ✔ More complex structure ✔ Mostly replaced by Hooks 🔹 Why Components Matter? 🔁 Reusable code 📂 Organized structure 🚀 Faster development #ReactComponents #ReactJS #FrontendDevelopment #JavaScript

The Ultimate React JS Cheat Sheet Every Developer Needs in 2026 Struggling to remember all React concepts during interviews or while building projects? Here's a power-packed React JS Cheat Sheet that puts everything in one place from basics to advanced topics so you can code faster and smarter Mastering React becomes easier when you have the right concepts at your fingertips. Here's a quick cheat sheet to boost your productivity and quick guide will help you revise, build, and crack interviews with confidence 700 Pro Tip: Don't just read-build projects using these concepts to truly master React! Save this post & follow for more developer-friendly #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #ReactHooks #Coding #SoftwareEngineering #UIDevelopment

🚀 𝗦𝘁𝗼𝗽 𝗚𝗼𝗼𝗴𝗹𝗶𝗻𝗴 𝗥𝗲𝗮𝗰𝘁 𝘀𝘆𝗻𝘁𝗮𝘅 𝗮𝗴𝗮𝗶𝗻 𝗮𝗻𝗱 𝗮𝗴𝗮𝗶𝗻... What if you had everything in one place? 👇 I’ve created a React.js Cheat Sheet to help you build faster and code smarter ⚛️ 📚 What’s inside: • JSX fundamentals • Core React concepts • Essential Hooks (useState, useEffect & more) 💡 Who is this for? ✔ Beginners getting started with React ✔ Developers preparing for interviews ✔ Engineers who want faster development & cleaner code 📌 Pro Tip: Great developers don’t memorize everything… They build systems and references they can rely on 💾 Save this post so you don’t have to search again while building 💬 Let’s discuss: What was the most confusing React concept when you started? 👨💻 Follow for more dev content #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #ReactHooks #CodingLife #DevTips #SoftwareEngineering

🎯 Struggling to wrap your head around React concepts? 🎯 🚀 These handwritten notes simplify complex topics and make learning React.js more visual and intuitive. Covers JSX, components, hooks, props, state, and more. Ideal for quick revision and frontend interview prep. 🔻 Why these are a must-have: Visual Learning: Perfect for those who find standard docs too dry. Beginner Friendly: Great for starting your React journey. Revision Ready: Crisp breakdowns of State vs. Props. If you’re preparing for frontend interviews, these notes are a valuable addition to your study resources. Repost and share with others to help them upskill! 📌 Save this post for your next study session. 💬 Comment "REACT" if you want the PDF version! 🔁 Repost to help others in your network grow! 📌All credit goes to the original creator of the material, Shared here for learning purposes only. #ReactJS #Frontend #WebDevelopment #JavaScript #Coding