Saurav Kumar’s Post

🔍 𝗪𝗵𝗮𝘁 𝗶𝘀 𝘁𝗵𝗲 𝗖𝗮𝗹𝗹 𝗦𝘁𝗮𝗰𝗸? The Call Stack is a LIFO (Last In, First Out) data structure that JavaScript uses to track function execution. Every time a function is called, it’s pushed onto the stack, and once executed, it’s popped off. 📘 𝗘𝘅𝗮𝗺𝗽𝗹𝗲: function first() {   console.log("First");   second(); } function second() {   console.log("Second"); } first(); 𝗘𝘅𝗲𝗰𝘂𝘁𝗶𝗼𝗻 𝗙𝗹𝗼𝘄: 1️⃣ first() is pushed to the stack 2️⃣ console.log("First") runs 3️⃣ second() is called → pushed to stack 4️⃣ console.log("Second") runs → popped from stack 5️⃣ first() finishes → popped from stack ⚡ 𝗪𝗵𝗮𝘁 𝗶𝘀 𝘁𝗵𝗲 𝗘𝘃𝗲𝗻𝘁 𝗟𝗼𝗼𝗽? JavaScript is single-threaded, meaning it executes one task at a time. The Event Loop allows JS to handle asynchronous tasks like setTimeout, fetch, or DOM events without blocking the main thread. 𝗜𝘁 𝘄𝗼𝗿𝗸𝘀 𝗹𝗶𝗸𝗲 𝘁𝗵𝗶𝘀: 1. JS executes synchronous code in the Call Stack. 2. Asynchronous tasks are sent to Web APIs (like timers, HTTP requests). 3. Once ready, callbacks are queued in the Callback/Task Queue. 4. The Event Loop continuously checks if the Call Stack is empty — if yes, it pushes the next callback from the queue. 📘 𝗘𝘅𝗮𝗺𝗽𝗹𝗲: console.log("Start"); setTimeout(() => {   console.log("Inside Timeout"); }, 0); console.log("End"); 𝗢𝘂𝘁𝗽𝘂𝘁: Start   End   Inside Timeout Even with 0ms, setTimeout runs after the current stack is empty — that’s the Event Loop in action! 💡 𝗪𝗵𝘆 𝗧𝗵𝗶𝘀 𝗠𝗮𝘁𝘁𝗲𝗿𝘀 ✅ Helps you write non-blocking, performant code ✅ Explains tricky behaviors like async/await, promises, and timers ✅ Essential for interview questions — every JS developer should master it 🧠 𝗧𝗼𝗽 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄 𝗤𝘂𝗲𝘀𝘁𝗶𝗼𝗻 #𝟯: Q: Explain the Event Loop in JavaScript. A: The Event Loop is a mechanism that allows JS to handle asynchronous operations. It monitors the Call Stack and Callback Queue, ensuring that async callbacks are executed only when the stack is empty. 🎯 𝗞𝗲𝘆 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆𝘀: 1. JS is single-threaded, but async tasks are handled via the Event Loop. 2. The Call Stack manages execution context in LIFO order. 3. Understanding this prevents bugs related to timers, async code, and promise chaining. Comment if you’ve ever been confused why setTimeout(..., 0) doesn’t run immediately! #JavaScript #EventLoop #CallStack #AsyncJS #WebDevelopment #NodeJS #InterviewPreparation #TechTips #JavaScriptInterviewQuestions #FrontendDevelopment #CodingTips #AsyncProgramming

Optional chaining is one of JavaScript's most useful features. But what's the performance impact? TL;DR it's massive. I recently collaborated with Simone Sanfratello on detailed benchmarks comparing noop functions to optional chaining, and the results were revealing: noop functions are 5.5x to 8.8x faster. Running 5 million iterations clearly showed the differences. Noop functions achieved 939M ops/sec as the baseline. Optional chaining with empty objects ran at 134M ops/sec (7x slower). Optional chaining with an existing method reached 149M ops/sec (6.3x slower). Deep optional chaining was the slowest, at 106M ops/sec (8.8x slower). The explanation comes down to what V8 must do. Noop functions are inlined by V8, making them essentially zero-overhead. The function call vanishes in optimized code. Optional chaining requires property lookup and null/undefined checks at runtime. V8 can't optimize these away because the checks must occur each time. This is why Fastify uses the abstract-logging module. Instead of checking logger?.info?.() throughout the code, Fastify provides a noop logger object with all logging methods as noop functions. The key is to provide noops upfront rather than checking for existence later. When logging is disabled, V8 inlines these noop functions at almost zero cost. With optional chaining, runtime checks are required every time. One reason for excessive optional chaining is TypeScript's type system encourages defensive coding. Properties are marked as potentially undefined even when runtime guarantees they exist, causing developers to add ?. everywhere to satisfy the type checker. The solution is better type modeling. Fix your interfaces to match reality, or use noop fallbacks like "const onRequest = config.hooks.onRequest || noop" and call it directly. Don't let TypeScript's cautious type system trick you into unnecessary defensive code. Context matters, though. Even "slow" optional chaining executes at 106+ million operations per second, which is negligible for most applications. Use optional chaining for external data or APIs where the structure isn't controlled, in normal business logic prioritizing readability and safety, and to reduce defensive clutter. Use noop functions in performance-critical paths, when code runs thousands of times per request, in high-frequency operations where every microsecond counts, and when you control the code and can guarantee function existence. Even a few thousand calls per request make the performance difference significant. My advice: don't optimize prematurely. Write your code with optional chaining where it enhances safety and clarity. For most applications, the safety benefits outweigh the performance costs. If profiling reveals a bottleneck, consider switching to noop functions. Profile first, optimize second. Remember: readable, maintainable code often surpasses micro-optimizations. But when those microseconds matter, now you understand the cost.

JavaScript Silent Errors — why they sneak up on you (and how to stop them) 🕵️♂️💥 Silent errors are bugs that don’t crash your app or throw a clear error — they just do the wrong thing and quietly ruin your day. Here are the most common culprits, short examples, and quick fixes you can start using today. What “silent” looks like Your function returns undefined instead of the object you expected. An assignment quietly fails (but code keeps running). A promise rejection never gets handled and silently breaks a flow. You swallow errors in an empty catch block. Tiny examples that bite 1. Forgotten return in arrow with block body const getUser = () => { name: 'Akin' }; // NOT returning the object console.log(getUser()); // undefined — no exception, just wrong // Fix: use parentheses or an explicit return const getUser2 = () => ({ name: 'Akin' }); 2. Assignment to non-writable property (non-strict mode = silent) const o = {}; Object.defineProperty(o, 'x', { value: 1, writable: false }); o.x = 2; // no error in non-strict mode — assignment ignored console.log(o.x); // 1 // Fix: use 'use strict' or check property descriptors 3. Swallowed error try { JSON.parse(badData); } catch (e) { // silently ignored — you never know parsing failed } // Fix: log/handle, or rethrow 4. Unhandled promise rejection (can be quiet) fetch('/api/thing') .then(r => r.json()); // no .catch -> rejection may be missed // Fix: always .catch() or use try/catch with async/await How to catch these earlier (practical checklist) Enable strict mode: use strict (or use modules — they’re strict by default). Use linters: ESLint with rules like no-empty, no-implicit-globals, no-unused-vars. Type safety: adopt TypeScript or Flow to catch wrong shapes/returns. Don’t swallow errors: never leave empty catch blocks — log or handle them. Always handle promises: .catch() or try { await ... } catch (e) { ... }. Add global handlers: window.addEventListener('unhandledrejection', e => console.error(e)); window.onerror = (msg, src, line, col, err) => { ... } DevTools: enable “Pause on exceptions” and break on caught exceptions during debugging. Tests & CI: unit tests + linting in CI stop regressions before they hit users. Error monitoring: Sentry/Rollbar/Bugsnag to surface production silent failures. Quick habits that pay off Log meaningful errors (include stack + context). Fail fast — prefer throwing or returning explicit errors instead of hiding failures. Small focused functions: easier to test and reason about. Code reviews: a second pair of eyes spots “weird but not crashing” issues. Wrap-up Silent errors are the worst because they’re invisible — make noise for them. Add linting + strict mode + promise handling + some basic monitoring and you’ll catch 90% of them early. #codecraftbyaderemi #webdevelopment #javascripterrors #learnJS #javascript

Let’s talk about something that’s quietly changing how we write and debug JavaScript: The Power of Optional Chaining and Nullish Coalescing If you’ve ever battled nested objects in JavaScript and spent precious minutes guarding against null or undefined errors, optional chaining and nullish coalescing might just become your new best friends. Here’s the scenario: You’re working with data from APIs, user inputs, or third-party services. Sometimes, part of the data might be missing or undefined, and directly accessing deep properties can throw nasty runtime errors like “Cannot read property 'x' of undefined.” Enter optional chaining: a syntax that lets you safely access deeply nested properties without writing bulky checks. How does it look in code? Imagine you have user data that might or might not have an address object: ```javascript const user = { name: 'Jane', address: { city: 'Seattle', } }; // Traditional way const city = user && user.address && user.address.city; console.log(city); // Seattle // With optional chaining const cityOpt = user?.address?.city; console.log(cityOpt); // Seattle ``` Notice how much cleaner that is? If address is missing, cityOpt will gracefully be undefined instead of throwing an error. Now, what about default values when something is null or undefined? That’s where nullish coalescing (??) comes in. Unlike the OR operator (||), which treats many falsy values like 0 or '' as false, nullish coalescing only triggers when the value is null or undefined. Example: ```javascript const config = { timeout: 0, }; const timeout = config.timeout || 3000; // results in 3000 — not ideal if 0 is valid const timeoutFixed = config.timeout ?? 3000; // results in 0 — correct handling console.log(timeout, timeoutFixed); ``` Optional chaining + nullish coalescing together reduce boilerplate, make your code easier to read, and prevent subtle bugs. If you haven’t adopted these yet, I advise giving them a try in your next project. They’re supported in all modern browsers and Node.js versions, and once you get the hang of them, your JavaScript will feel smoother and safer. Ready to write cleaner, more robust JS? Start chaining safely today. #JavaScript #WebDevelopment #CodingTips #CleanCode #SoftwareEngineering #TechTrends #DevCommunity #Programming

🔗 SK – Promise Chain: Sequential Data Fetching in JavaScript 💡 Explanation (Clear + Concise) Sometimes, you need to fetch data in sequence — for example, when the result of one API depends on another. That’s where Promise chaining shines. 🧩 Real-World Example (Code Snippet) // 🧠 Simulated APIs function getUser() { return Promise.resolve({ id: 1, name: "Sasi" }); } function getPosts(userId) { return Promise.resolve([`Post1 by User ${userId}`, `Post2 by User ${userId}`]); } // 🔗 Chaining Promises getUser() .then(user => { console.log("User:", user.name); return getPosts(user.id); }) .then(posts => { console.log("Posts:", posts); }) .catch(err => console.error(err)); // ⚙️ Modern async/await async function fetchData() { const user = await getUser(); const posts = await getPosts(user.id); console.log("Async/Await:", posts); } fetchData(); ✅ Why It Matters in React: Manage sequential API calls in effects or Redux Thunks. Cleaner logic for dependent API requests. Simplifies asynchronous workflows in modern React apps. 💬 Question: Do you prefer Promise chains or async/await in your React projects — and why? 📌 Follow Sasikumar S for more daily dev reflections, real-world coding insights & React mastery. 🤝 Connect Now: sasiias2024@gmail.com 💟 Visit: sk-techland.web.app ❤️ Follow our LinkedIn Page for more React & JavaScript growth tips. #JavaScript #ReactJS #Promises #AsyncAwait #FrontendDeveloper #WebDevelopment #JSFundamentals #CareerGrowth #CodingJourney

💡 𝗝𝗮𝘃𝗮𝗦𝗰𝗿𝗶𝗽𝘁 𝗘𝘃𝗲𝗻𝘁 𝗟𝗼𝗼𝗽 — 𝗧𝗵𝗲 𝗥𝗲𝗮𝘀𝗼𝗻 𝗬𝗼𝘂𝗿 𝗖𝗼𝗱𝗲 𝗗𝗼𝗲𝘀𝗻’𝘁 𝗥𝘂𝗻 𝗶𝗻 𝗢𝗿𝗱𝗲𝗿⚙️ Most developers know about the Event Loop, but few truly understand how JavaScript executes your code step by step — from the Global Execution Context to Web APIs, Task Queues, and Microtasks 🌀 Let’s break it down like a system engineer 👇 🧠 𝗛𝗼𝘄 𝗶𝘁 𝗦𝘁𝗮𝗿𝘁𝘀 — 𝗧𝗵𝗲 𝗚𝗹𝗼𝗯𝗮𝗹 𝗘𝘅𝗲𝗰𝘂𝘁𝗶𝗼𝗻 𝗖𝗼𝗻𝘁𝗲𝘅𝘁 When JavaScript runs, it first creates a Global Execution Context (GEC) — this contains: -> the Memory Component (variables, functions) -> the Code Component (thread of execution) It’s stored in the Call Stack, which works on a simple principle — LIFO (Last In, First Out). ⚙️ 𝗪𝗵𝗮𝘁 𝗛𝗮𝗽𝗽𝗲𝗻𝘀 𝗪𝗵𝗲𝗻 𝗬𝗼𝘂 𝗖𝗮𝗹𝗹 𝗮 𝗧𝗶𝗺𝗲𝗿 𝗼𝗿 𝗔𝗣𝗜 The browser (or Node.js) provides Web APIs like: -> setTimeout -> fetch -> DOM events These are not part of JS itself — they are handled by the environment. Once completed, their callbacks move to the Task Queues. 🧩 𝗧𝘆𝗽𝗲𝘀 𝗼𝗳 𝗧𝗮𝘀𝗸 𝗤𝘂𝗲𝘂𝗲𝘀 1️⃣ Macrotask Queue (Task Queue): Contains → setTimeout, setInterval, setImmediate, fetch callbacks, and DOM events. 2️⃣ Microtask Queue: Contains → Promise.then, async/await, and process.nextTick (Node.js). ⚡ 𝗧𝗵𝗲 𝗘𝘃𝗲𝗻𝘁 𝗟𝗼𝗼𝗽 — 𝗧𝗵𝗲 𝗕𝗿𝗮𝗶𝗻 𝗼𝗳 𝗜𝘁 𝗔𝗹𝗹 After every macrotask, the Event Loop checks the Microtask Queue — and executes all microtasks before picking up the next macrotask. Why? Because microtasks are usually short, immediate reactions (like resolved Promises) and must run before the next rendering or I/O task. 🧩 𝗤𝘂𝗶𝗰𝗸 𝗗𝗲𝗺𝗼 console.log("Start"); setTimeout(() => console.log("Macrotask"), 0); Promise.resolve().then(() => console.log("Microtask")); console.log("End"); 📤 Output: Start End Microtask Macrotask ✅ The Microtask Queue (Promise) runs before Macrotask Queue (setTimeout). 💭 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆: JavaScript is single-threaded, but not blocking — thanks to the event loop and task queues managing concurrency intelligently⚙️ Understanding this flow separates coders from engineers. #JavaScript #EventLoop #FrontendDevelopment #AsyncProgramming #WebDevelopment #FrontendEngineer #100DaysOfCode #SoftwareEngineering #TechLearning #Coding

🚀 𝗗𝗔𝗬 𝟰8/𝟭𝟬𝟬 - #𝗟𝗲𝗮𝗿𝗻𝗜𝗻𝗣𝘂𝗯𝗹𝗶𝗰 (𝗙𝗼𝗰𝘂𝘀: 𝗡𝗼𝗱𝗲.𝗷𝘀, 𝗕𝗮𝗰𝗸𝗲𝗻𝗱 & 𝗦𝘆𝘀𝘁𝗲𝗺 𝗗𝗲𝘀𝗶𝗴𝗻) 🧠 Today's Focus: 𝗹𝗶𝗯𝘂𝘃 & 𝗔𝘀𝘆𝗻𝗰 𝗜/𝗢 - The Secret Sauce of Node.js 📝 Introduction Today I dove deep into 𝗹𝗶𝗯𝘂𝘃 - the powerful C library that gives Node.js its superpowers for handling asynchronous operations. Understanding this is key to mastering Node.js performance! ⚡ The JavaScript Paradox 🔹 JavaScript is synchronous & single-threaded - executes code line by line 🔹 But Node.js handles async operations - how? Enter libuv! 🎯 What is libuv? ✅ C library that provides async I/O capabilities ✅ Manages the Event Loop in Node.js ✅ Handles OS operations that JavaScript can't do alone ✅ The bridge between V8 engine and operating system 🔄 How libuv Works with Node.js [Your JavaScript Code]   → [V8 Engine]   → [libuv - Event Loop]   → [OS Operations]  → [Callback Queue]  → [Back to V8] 📊 libuv's Superpowers: 🔹 File System Operations - reading/writing files 🔹 Network Operations - HTTP requests, sockets 🔹 Timers - setTimeout, setInterval 🔹 Child Processes - spawning other programs 🔹 Signal Handling - process signals 🎪 𝗧𝗵𝗲 𝗘𝘃𝗲𝗻𝘁 𝗟𝗼𝗼𝗽 𝗶𝗻 𝗔𝗰𝘁𝗶𝗼𝗻 Synchronous Code: javascript let a = 10786; let b = 20987; let c = a * b; // Executes immediately in call stack Asynchronous Code: javascript setTimeout(() => {  console.log("This waits!"); // Handled by libuv }, 1000); fs.readFile("file.txt", (data) => {  console.log(data); // libuv manages file reading }); ⚡ Why This Architecture Rocks: ✅ Non-blocking I/O - No waiting for slow operations ✅ Single thread, massive concurrency - Handles 10K+ connections ✅ Optimal resource usage - No thread creation overhead ✅ Perfect for I/O-heavy apps - APIs, databases, file operations 🚨 Key Insight: JavaScript engine alone can only run synchronous code. With libuv, it gains the power to handle async operations efficiently through the event loop! 🙏 𝗦𝗽𝗲𝗰𝗶𝗮𝗹 𝗧𝗵𝗮𝗻𝗸𝘀 Huge thanks to Akshay Saini 🚀 — his Namaste Node.js series makes backend concepts crystal clear. 🎥 Watch here: https://lnkd.in/gKA8Du6u 💬 𝗪𝗮𝗻𝘁 𝗺𝘆 𝗵𝗮𝗻𝗱𝘄𝗿𝗶𝘁𝘁𝗲𝗻 𝗻𝗼𝘁𝗲𝘀 👉 Comment “𝗡𝗼𝗱𝗲𝗷𝘀 𝗻𝗼𝘁𝗲𝗱” 💬 Any other Node.js or backend resource you’d recommend? Drop it below ⬇️ 👋 Explore more free 𝗡𝗼𝗱𝗲𝗷𝘀 / 𝗔𝗜 / 𝗠𝗟 resources on my profile. 📌 Repost to help others understand Node.js architecture! ♻️ Share to help your network learn how JavaScript runs on servers! 📌 𝗕𝗼𝗻𝘂𝘀: I’ve shared 𝟭𝟬𝟬+ 𝘀𝗶𝗺𝗶𝗹𝗮𝗿 𝗳𝗿𝗲𝗲 Node/ 𝗔𝗜 𝗿𝗲𝘀𝗼𝘂𝗿𝗰𝗲𝘀 on my profile — check them out if you love learning from the best minds in tech and academia. 👤 Follow Saddam Arbaa for insights on 𝗡𝗼𝗱𝗲.𝗷𝘀, 𝗦𝘆𝘀𝘁𝗲𝗺 𝗗𝗲𝘀𝗶𝗴𝗻, 𝗔𝗜/𝗠𝗟, 𝗠𝗟𝗢𝗽𝘀, 𝗔𝗜 𝗔𝗴𝗲𝗻𝘁𝘀, and hands-on developer tools. #NodeJS #JavaScript #Backend #Programming #Coding #SoftwareEngineer #DevCommunity #LearnInPublic #CareerGrowth #AIEngineering #JobSearch #OpenToWork

Day 77 of 100DaysOfCode – Understanding Async/Await, JS Engine & Geolocation API 🌍 Let’s break down three key JavaScript concepts every developer should understand 👇 🔹 1. What Is Async/Await, and How Does It Work? JavaScript is asynchronous — meaning it doesn’t wait for long tasks like fetching data or file reading to finish before moving on. That’s where async/await shines. It makes async code look simple and readable, like synchronous code. async function delayedGreeting(name) { console.log("A Messenger entered the chat..."); await new Promise(resolve => setTimeout(resolve, 2000)); console.log(`Hello, ${name}!`); } delayedGreeting("Alice"); console.log("First Printed Message!"); Here, the function pauses for 2 seconds before greeting Alice — but the rest of the program keeps running! We can also handle errors neatly using try/catch: async function fetchUserData() { try { let response = await fetch(`https://lnkd.in/dWvHabH4); let userData = await response.json(); console.log(userData); } catch (error) { console.log("Error fetching user data:", error); } } Async/await = cleaner syntax + better error handling ✨ 🔹 2. How Does the JavaScript Engine Work (and What Is a Runtime)? Think of the JavaScript engine as the “brain” that reads, understands, and executes your code. For example, Google Chrome and Node.js use the V8 Engine. When you run: const greeting = "Hello, World!"; console.log(greeting); The engine: Parses the code (checks for errors) Compiles it into machine-readable bytecode Executes it to print “Hello, World!” But the JavaScript runtime is more than just the engine — it’s the whole environment your code runs in. In the browser → runtime includes the DOM, Fetch API, and timers. In Node.js → runtime includes file systems, HTTP, etc. So the engine executes, while the runtime provides tools to interact with the outside world 🌍 🔹 3. What Is the Geolocation API and How Does getCurrentPosition Work? The Geolocation API lets websites request your location — but only with your permission (for privacy reasons). Example: navigator.geolocation.getCurrentPosition( (position) => { console.log("Latitude: " + position.coords.latitude); console.log("Longitude: " + position.coords.longitude); }, (error) => { console.log("Error: " + error.message); } ); This uses your device’s GPS, Wi-Fi, or IP address to determine your location. You get a position object that contains details like: latitude longitude accuracy altitude, and more. Always explain why your app needs location data and how it’ll be used — user trust is key. 💡 Wrap-Up: Async/Await simplifies asynchronous programming. JavaScript Engine executes code; Runtime gives it superpowers. Geolocation API helps apps know “where” the user is — responsibly.

🔥 𝐀𝐬𝐲𝐧𝐜𝐡𝐫𝐨𝐧𝐨𝐮𝐬 𝐉𝐚𝐯𝐚𝐒𝐜𝐫𝐢𝐩𝐭 & 𝐄𝐕𝐄𝐍𝐓 𝐋𝐎𝐎𝐏 — 𝐄𝐱𝐩𝐥𝐚𝐢𝐧𝐞𝐝 𝐟𝐫𝐨𝐦 𝐒𝐜𝐫𝐚𝐭𝐜𝐡! ⚙️ 𝐓𝐡𝐞 𝐉𝐚𝐯𝐚𝐒𝐜𝐫𝐢𝐩𝐭 𝐄𝐧𝐠𝐢𝐧𝐞 𝐚𝐧𝐝 𝐂𝐚𝐥𝐥 𝐒𝐭𝐚𝐜𝐤 • JavaScript is a synchronous, single-threaded language, meaning it has one Call Stack where all code execution happens sequentially, one line at a time. • Execution starts with the Global Execution Context being pushed onto the Call Stack. • Function invocations also create their own execution contexts which are pushed onto and then popped off the Call Stack. -------- 🌐 𝐁𝐫𝐨𝐰𝐬𝐞𝐫 𝐒𝐮𝐩𝐞𝐫𝐩𝐨𝐰𝐞𝐫𝐬 (𝐖𝐞𝐛 𝐀𝐏𝐈𝐬) • The browser (or Node.js environment) provides extra capabilities beyond the JavaScript engine, known as Web APIs. • Examples of Web APIs include: setTimeout, the DOM (Document Object Model), fetch (for network requests), and localStorage. • These APIs allow JavaScript code to perform non-blocking (asynchronous) task. ------- 🔁 𝐓𝐡𝐞 𝐄𝐯𝐞𝐧𝐭 𝐋𝐨𝐨𝐩, 𝐂𝐚𝐥𝐥𝐛𝐚𝐜𝐤 𝐐𝐮𝐞𝐮𝐞, 𝐚𝐧𝐝 𝐌𝐢𝐜𝐫𝐨𝐭𝐚𝐬𝐤 𝐐𝐮𝐞𝐮𝐞 • When an asynchronous function like 𝐬𝐞𝐭𝐓𝐢𝐦𝐞𝐨𝐮𝐭 or an 𝐞𝐯𝐞𝐧𝐭 𝐥𝐢𝐬𝐭𝐞𝐧𝐞𝐫 (𝐚𝐝𝐝𝐄𝐯𝐞𝐧𝐭𝐋𝐢𝐬𝐭𝐞𝐧𝐞𝐫) is encountered: 1. The function itself is handled by the browser's Web API environment. 2. The callback function (the code to be executed later) is registered. • Once the 𝐚𝐬𝐲𝐧𝐜𝐡𝐫𝐨𝐧𝐨𝐮𝐬 𝐭𝐚𝐬𝐤is complete (e.g., the timer expires, or a button is clicked): The registered callback function is moved to the 𝐂𝐚𝐥𝐥𝐛𝐚𝐜𝐤 𝐐𝐮𝐞𝐮𝐞 (𝐚𝐥𝐬𝐨 𝐤𝐧𝐨𝐰𝐧 𝐚𝐬 𝐭𝐡𝐞 𝐓𝐚𝐬𝐤 𝐐𝐮𝐞𝐮𝐞 𝐨𝐫 𝐌𝐚𝐜𝐫𝐨𝐭𝐚𝐬𝐤 𝐐𝐮𝐞𝐮𝐞). • The 𝐄𝐯𝐞𝐧𝐭 𝐋𝐨𝐨𝐩 is a continuously running process that checks two main things: • Is the Call Stack empty? (i.e., is all synchronous code finished executing?) • If the Call Stack is empty, are there any functions waiting in the Callback Queue or Microtask Queue? • If the Call Stack is empty, the Event Loop picks a function from the queues and pushes it onto the Call Stack for execution. --------- ⚡ 𝐌𝐢𝐜𝐫𝐨𝐭𝐚𝐬𝐤𝐬 𝐯𝐬. 𝐌𝐚𝐜𝐫𝐨𝐭𝐚𝐬𝐤𝐬 • 𝐌𝐢𝐜𝐫𝐨𝐭𝐚𝐬𝐤 𝐐𝐮𝐞𝐮𝐞 (Higher Priority): Holds callbacks from Promises (like .then() and .catch()) and Mutation Observers. •𝐂𝐚𝐥𝐥𝐛𝐚𝐜𝐤 𝐐𝐮𝐞𝐮𝐞 (Lower Priority): Holds callbacks from Web APIs like setTimeout, setInterval, and DOM event listeners. 1. 𝐌𝐢𝐜𝐫𝐨𝐭𝐚𝐬𝐤𝐬 𝐡𝐚𝐯𝐞 𝐚 𝐡𝐢𝐠𝐡𝐞𝐫 𝐩𝐫𝐢𝐨𝐫𝐢𝐭𝐲. The Event Loop will empty the entire Microtask Queue before it checks and pushes one single task from the Callback Queue onto the Call Stack. 2. If the Microtask Queue keeps adding new microtasks indefinitely, it can lead to 𝐒𝐭𝐚𝐫𝐯𝐚𝐭𝐢𝐨𝐧of the Callback Queue, preventing those tasks from ever running. -------- 🎥 Highly recommend this episode if you want to understand how JavaScript handles async code under the hood!⚡ https://lnkd.in/dpTTnJWx #JavaScript #NamasteJavaScript #EventLoop #WebDevelopment #AsyncJS #FrontendDevelopment #AkshaySaini #JavascriptMastery

Key Features of React.js v19.0 React v19.0, which has introduced several major updates focused on improving performance, simplifying common development patterns, and enhancing the developer experience. The most significant features include: New Hooks and APIs React 19 introduces new utilities to handle data fetching, form state, and UI updates more efficiently: use API: A new API that allows you to read the value of resources like Promises or Context directly within the render phase, eliminating the need for some useEffect or complex data-fetching patterns. Actions & Form Hooks: This set of features streamlines form handling: Actions: Functions (can be async) passed to form elements (e.g., <form action={actionFunction}>) that automatically manage pending states and error handling using Transitions. useActionState (formerly useFormState): A hook to manage the state and result of an Action. useFormStatus: A hook for child components to read the submission status (pending, data, etc.) of their parent <form>. useOptimistic: A hook for implementing Optimistic UI updates, where the UI instantly reflects the expected outcome of an asynchronous action while the network request is still in progress. Performance and Rendering Enhancements React Compiler (React Forget): An experimental feature aimed at automating memoization. When released, it will compile React code to plain JavaScript, automatically determining when to skip re-renders, potentially eliminating the need for manual use of memo, useMemo, and useCallback in most cases. Server Components & Actions: Features designed to improve initial page load times and simplify data fetching by rendering components and executing data mutations on the server. New directives: 'use client' (marks client-side code) and 'use server' (marks server-side functions callable from client code). Ref as a Prop: Functional components can now directly accept the ref prop, which often removes the need for the forwardRef Higher-Order Component. Asset Loading: Native support for rendering and managing <script>, <link>, and <title> tags within components, which helps React coordinate the loading of resources like stylesheets and async scripts. Developer Experience & Compatibility Improved Hydration Error Reporting: React 19 provides clearer, single error messages with a diff of the mismatched content between server-rendered and client-side HTML, making debugging easier. Support for Web Components/Custom Elements: Enhanced compatibility for integrating custom HTML elements into React applications. Context as a Provider: You can now render a Context object directly as a provider (e.g., <ThemeContext value="dark">) instead of using <ThemeContext.Provider>. React 19 makes significant moves toward simplifying asynchronous data and form handling while laying the groundwork for automatic performance optimization with the React Compiler.