Understanding the Event Loop in JavaScript

𝗖𝗮𝗻 𝗬𝗼𝘂 𝗚𝘂𝗲𝘀𝘀 𝘁𝗵𝗲 𝗢𝘂𝘁𝗽𝘂𝘁 𝗼𝗳 𝗧𝗵𝗶𝘀 𝗝𝗮𝘃𝗮𝗦𝗰𝗿𝗶𝗽𝘁 𝗖𝗼𝗱𝗲? function demo() {  console.log("Function start");  setTimeout(() => console.log("Inside setTimeout (macrotask)"), 0);  Promise.resolve().then(() => console.log("Inside Promise (microtask)"));  console.log("Function end"); } console.log("Start"); demo(); console.log("End"); Can You Guess the Output? Take a moment before scrolling 𝗢𝘂𝘁𝗽𝘂𝘁: Start   Function start   Function end   End   Inside Promise (microtask)   Inside setTimeout (macrotask) 𝗘𝘅𝗽𝗹𝗮𝗻𝗮𝘁𝗶𝗼𝗻: Synchronous code first: Logs: Start → Function start → Function end → End All run immediately in the call stack. Async tasks are queued: setTimeout() → goes to the macrotask queue. Promise.then() → goes to the microtask queue. 𝗘𝘃𝗲𝗻𝘁 𝗹𝗼𝗼𝗽 𝗽𝗵𝗮𝘀𝗲: After synchronous code finishes, the event loop first checks the microtask queue → runs the Promise callback. Then it moves to the macrotask queue → runs the timeout callback. So the flow is: Call Stack → Microtasks → Macrotasks → Repeat 𝗜𝗳 𝗬𝗼𝘂’𝗿𝗲 𝗮 𝗥𝗲𝗮𝗰𝘁 𝗗𝗲𝘃𝗲𝗹𝗼𝗽𝗲𝗿... This same concept drives React’s internal scheduling and rendering. When you call setState(), React doesn’t update the UI immediately it queues that update and batches it efficiently in the next event loop cycle. Understanding the event loop helps you reason about:  • Why some state updates seem delayed  • How useEffect and useLayoutEffect differ in timing  • Why React batches multiple updates together If you get this concept, you’re not just writing React  you’re thinking like React. #JavaScript #React #Frontend #WebDevelopment #Async #EventLoop #ProgrammingConcepts

🎮 Tic-Tac-Toe — built from scratch using JavaScript! Clean UI, instant win detection, and restart functionality — no frameworks, just pure logic. This project helped me sharpen my DOM handling and problem-solving skills. 💻 Check out the code and try playing! #webdev #javascriptprojects #frontend #developerjourney

The Popover API simplifies a common frontend task: menus, dialogs, tooltips. What used to take 30+ lines of JavaScript like managing state, accessibility, and event listeners, now can be done in just a few lines of HTML. It’s cleaner, more accessible, and reduces boilerplate. I’ve put together a before/after comparison to show how this changes day-to-day UI work 👇 #webdev #frontend #javascript #css

⚛️ React Design Patterns 🎨 ✔ HOCs → Legacy way of code reuse (still useful in some cases, but hooks are better). ✔ Render Props → Flexible logic sharing, but can get verbose. ✔ Compound Components → Clean APIs (Tabs, Select, Modals) using Context. ✔ Controlled vs Uncontrolled → Choose wisely based on DX vs flexibility. ✔ Custom Hooks & Provider Pattern → Modern React’s backbone for abstraction + state sharing. 💡 Think of it as: Design patterns are the language that makes React codebases readable, scalable, and consistent across teams. Without them → spaghetti components that are hard to maintain. With them → intentional, declarative APIs that scale with product complexity. #ReactJS #JavaScript #FrontendDevelopment #Scalability #100DaysOfReact

🧠 Understanding the JavaScript Event Loop JavaScript is single-threaded, yet it seamlessly handles multiple operations such as fetching data, waiting for timers, and updating the UI — all without freezing the browser. The mechanism that enables this concurrency is the Event Loop. Here’s how it works 👇 1️⃣ JavaScript executes code sequentially in the Call Stack. 2️⃣ When it encounters asynchronous operations (setTimeout, fetch, event listeners, etc.), these are delegated to the Web APIs. 3️⃣ Once the async operations complete, their callbacks are queued in either the Microtask Queue or the Task Queue. 4️⃣ The Event Loop continuously checks if the call stack is empty. ✔️ If it is, all microtasks (e.g., Promises, queueMicrotask, process.nextTick) are executed first. ✔️ Once the microtasks are done, the Event Loop processes one macrotask (e.g., setTimeout, setInterval, I/O tasks, or DOM events). 🔁 This cycle repeats continuously. ⚡ Task Priority: Microtasks have a higher priority than macrotasks. Even if a setTimeout is ready to execute, all pending promise callbacks (microtasks) will run first. 💡 Excessive chaining of microtasks can delay rendering or block subsequent tasks — use them carefully. #JavaScript #WebDevelopment #Frontend #React #AsyncProgramming #EventLoop #DeveloperInsights

🤔 Ever wondered… If JavaScript is single-threaded and the event loop executes one function at a time, then how do async operations actually work? That’s the beauty of JavaScript’s runtime model! 🚀 🔹 JavaScript itself runs on a single thread—it can only do one thing at a time. 🔹 But when we use async operations (like setTimeout, fetch, or Promises), the heavy lifting doesn’t block the main thread. 🔹 Instead, these operations are handed off to the browser’s Web APIs (or Node.js internals). 🔹 Once completed, their callbacks are queued in the task queue/microtask queue. 🔹 The event loop then picks them up when the call stack is free. So JavaScript never broke its single-threaded rule. Instead, it’s the event loop’s smart orchestration that makes it all look seamless and non-blocking. 🚀 #Javascript #Frontend #FrontendDevelopment #ReactJs #React

𝗥𝗲𝗮𝗰𝘁 𝗛𝗼𝗼𝗸𝘀 — 𝗧𝗵𝗲 𝗥𝗲𝘃𝗼𝗹𝘂𝘁𝗶𝗼𝗻 𝗧𝗵𝗮𝘁 𝗖𝗵𝗮𝗻𝗴𝗲𝗱 𝗛𝗼𝘄 𝗪𝗲 𝗕𝘂𝗶𝗹𝗱 𝗙𝗿𝗼𝗻𝘁𝗲𝗻𝗱𝘀 Before 𝗥𝗲𝗮𝗰𝘁 𝗛𝗼𝗼𝗸𝘀, React development was complex — class components, lifecycle methods, and tangled state logic. Hooks made React cleaner, simpler, and more powerful. And Custom Hooks? They took reusability and scalability to the next level. React Hooks didn’t just simplify code — They transformed how we think about component architecture. #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #ReactHooks #CustomHooks #CleanCode #SoftwareEngineering #DeveloperCommunity

🔥🧠 JavaScript Event Loop: Callback Queue vs Microtask Queue — The Ultimate Showdown! 🚀 In JS, async operations don’t just “wait” — they get queued! But not all queues are created equal ⚖️ 🕒 Callback Queue (aka Macrotask Queue): → Holds callbacks from: setTimeout, setInterval, DOM events, I/O, etc. → Processed ONE at a time after the call stack is EMPTY. → Lower priority in the event loop cycle. ⚡ Microtask Queue: → Holds: Promises (.then/.catch), queueMicrotask(), MutationObserver. → Processed IMMEDIATELY after current sync code — BEFORE the next macrotask! → Higher priority — runs to completion before anything from Callback Queue. 🎯 Key Difference: Microtasks jump the line! 🏃♂️💨 Even if a setTimeout(0) and Promise.resolve().then() are scheduled together, the Promise ALWAYS wins. 🆕 Modern Updates (ES2020+): → queueMicrotask() API gives devs direct access to microtask queue 🧬 → Browsers now strictly enforce microtask priority (no more sneaky setTimeout wins!) → Node.js v11+ aligns with browser behavior for consistency 🔄 💡 Pro Tip: Use microtasks for ultra-fast, high-priority async logic. Use macrotasks (setTimeout) when you want to yield control back to the browser (e.g., UI rendering). 🌐 Bottom Line: Event Loop ➡️ Call Stack ➡️ Microtasks (ALL!) ➡️ Render ➡️ Macrotasks (ONE!) ➡️ Repeat 🔄 #JavaScript #EventLoop #Microtask #CallbackQueue #AsyncJS #FrontendDev #WebDev #Promises #setTimeout #JSInternals

💡JavaScript Tip: 𝗨𝘀𝗲 𝗠𝗶𝗹𝗹𝗶𝗳𝘆 𝗳𝗼𝗿 𝗛𝘂𝗺𝗮𝗻-𝗙𝗿𝗶𝗲𝗻𝗱𝗹𝘆 𝗡𝘂𝗺𝗯𝗲𝗿𝘀. When displaying large numbers to users, readability matters; instead of showing long digits like 1250000, JavaScript now gives you a clean way to abbreviate them. #JavaScript #WebDevelopment #Frontend #Backend #JavaScriptTips #MobileDevelopment #Fullstack

🔴 𝗪𝗿𝗼𝗻𝗴 𝗖𝗼𝗱𝗲 𝘃𝘀 ✅ 𝗥𝗶𝗴𝗵𝘁 𝗖𝗼𝗱𝗲 𝗝𝗮𝘃𝗮𝗦𝗰𝗿𝗶𝗽𝘁 𝗘𝗿𝗿𝗼𝗿 𝗛𝗮𝗻𝗱𝗹𝗶𝗻𝗴 𝗗𝗼𝗻𝗲 𝗥𝗶𝗴𝗵𝘁 Most devs think they’re handling errors. But if your catch block just rethrows without context… you’re not handling anything. You're just playing hot potato with bugs. 🥔 I made a clean visual comparing common JS error-handling mistakes vs best practices. Split-screen. Syntax-highlighted. Developer aesthetic. Perfect for your next code review or team onboarding. 💡 𝗛𝗶𝗴𝗵𝗹𝗶𝗴𝗵𝘁𝘀: Don’t blindly throw e add context or handle it. Use finally for cleanup, not error logic. Rethrow only when necessary, and with purpose. #JavaScript #ErrorHandling #CleanCode #DevHumor #CodeReview #Frontend #WebDev #TechIllustration #angular