Mohamed Irfaan’s Post

Most developers say they “understand async JavaScript.” Most… don’t. And you can tell the difference the moment performance starts breaking. At a senior level, concepts like Web Workers, Promises, async/await, and the Event Loop aren’t just “things you know” — they’re tools you intentionally design with. Here’s the reality 👇 🚨 The Event Loop isn’t magic — it’s a constraint JavaScript is single-threaded. Always has been (ignoring workers). That means: One call stack One main thread Everything competes for it So when your app “lags”… it’s not random. You blocked the main thread. Period. ⚡ Promises & async/await don’t make things faster They make things non-blocking. Big difference. await fetchData(); This doesn’t “run in background.” It just tells the event loop: “I’ll come back later, don’t block the thread.” If your function is CPU-heavy? Congrats — you’re still freezing the UI. 🧠 Microtasks vs Macrotasks Promises → Microtask queue setTimeout / setInterval → Macrotask queue Microtasks always run before the next render. Which means: You can accidentally starve the UI if you chain too many promises. Yes, your “clean async code” can kill performance. 🔥 Web Workers = actual parallelism This is where things get real. Web Workers: Run on separate threads Don’t block the main thread Communicate via message passing Perfect for: Heavy computations Data processing Large JSON parsing Complex visual calculations (think maps, charts) But here’s the catch: You lose direct access to the DOM. So design matters. 🧩 Senior mindset shift Instead of asking: 👉 “How do I write async code?” Start asking: 👉 “What should NOT run on the main thread?” That’s the real game. 💡 Rule of thumb I follow IO-bound → Promises / async-await UI updates → Keep main thread clean CPU-heavy → Offload to Web Workers Most performance issues in frontend apps aren’t about React, Vue, or frameworks. They’re about misunderstanding how JavaScript actually runs. Master the runtime → everything else becomes easier. #javascript #webdevelopment #frontend #softwareengineering #performance #async #webworkers #seniorengineer #coding

#js #8 **Why JavaScript Is Single Threaded Synchronous Language** 🧠 Statement: 👉 “JavaScript is single-threaded and synchronous” We’ll break this into parts so it’s easy to understand. 🧵 1. What is Single-Threaded? 👉 JavaScript has only ONE main thread That means: One call stack One task at a time Example: console.log("A"); console.log("B"); console.log("C"); 👉 Output: A B C ✔ It runs one by one, not in parallel. ⚙️ Why JavaScript is single-threaded? Originally designed for browsers. Browsers (like Google Chrome) need to: Update UI Handle clicks 👉 If multiple threads changed UI at same time: UI would break Data would be inconsistent ✔ So JavaScript uses one thread → safe & predictable ⏱️ 2. What is Synchronous? 👉 Synchronous means: Code runs line by line, and each line waits for previous one to finish Example: console.log("Start"); function slowTask() { for (let i = 0; i < 1; i++) {} } slowTask(); console.log("End"); 👉 Output: Start End (after delay) ✔ End waits until slowTask finishes 🔴 Problem with synchronous nature If something takes time: Everything stops ⛔ UI freezes 👉 Bad user experience 🔄 3. Then how does JavaScript handle async? Here’s the important twist 👇 👉 JavaScript is: ✔ Single-threaded ✔ Synchronous (by default) ❗ BUT supports async using system outside JS 🌐 Behind the scenes JavaScript uses: Browser APIs Event system → Event Loop 📦 Example console.log("Start"); setTimeout(() => { console.log("Async"); }, 2000); console.log("End"); 🔄 Execution flow Start → runs setTimeout → sent to browser End → runs immediately After 2 sec → callback comes back Event loop executes it Output: Start End Async 👉 So JS looks async, but actually: It delegates work Still runs one task at a time 🧑🍳 Simple analogy You (JS) 👨🍳: Cook one dish at a time (single-threaded) Follow order (synchronous) Ask assistant to do waiting tasks (async) 👉 JavaScript is: ✔ Single-threaded One task at a time ✔ Synchronous (by default) Executes line by line ✔ Non-blocking (with help) Uses event loop + browser APIs 👉 JavaScript is single-threaded and synchronous, but uses the event loop to handle asynchronous operations without blocking execution. #Javascript #ObjectOrientedProgramming #SoftwareDevelopment

https://lnkd.in/dpSkdGET — Most senior devs are still writing JavaScript like it’s 2018, and it is quietly killing your app's performance. As a Senior Frontend Engineer working with TypeScript and React 19 daily, I’ve realized that the "standard" way of doing things is often outdated. I just released Part 98 of The Modern JavaScript Playbook—a massive 5,000+ word deep dive into the evolution of our ecosystem. While researching this piece, I found a surprising "modern baseline" shift. 💡 We often focus on 'includes javascript' logic or 'javascript if not' patterns for functional safety. But we’re ignoring how modern engines handle closures and memory during complex page transitions. I remember spending an entire weekend debugging a janky scroll animation on a production site. The culprit? A memory leak inside a hook that I thought was "standard" practice. 🧠 That mistake taught me that even with fast tools like Vite and Bun, our code patterns are the real bottleneck. In this playbook, I break down advanced design patterns, async/await pitfalls, and how to use Framer Motion with Tailwind CSS without destroying your frame rate. ⚡ It’s the comprehensive guide I wish someone had handed me when I started scaling frontend systems. 🛠️ It's time to move beyond basic tutorials and master the engineering behind the code. 📈 What is the one JavaScript concept that took you the longest to truly master? 🚀 #FrontendEngineer #TypeScript #ReactJS #JavaScript #WebDevelopment #SoftwareEngineering #Coding #Programming #FrontendEngineers #NextJS #WebPerf #CleanCode #JavaScriptTips #TechCommunity #SoftwareArchitecture #React19 #FramerMotion #TailwindCSS #ViteJS #BunJS #CodingLife #WebDevTips #JSPlaybook #AdvancedJavaScript #PerformanceOptimization #FullStackDev #ComputerScience #CodeQuality #DeveloperExperience #OpenSource #TechInsights #FrontendDev #WebDesign #UIUX #ModernWeb #SoftwareDev #TechTutorial #ProgrammingTutorial #LearningToCode #CodeNewbie #WebStandard #JavaScriptTutorial #EngineeringManager #TechLeader #SystemDesign #CodeOptimization #AsyncAwait #JavaScriptClosures #DesignPatterns #AnimationPerformance #DOMManipulation #HTML5 #CSS3 #ES6 #TypeScriptTips #WebApps #SoftwareEngineerLife #JuniorToSenior #TechCareer #DevOps #CloudComputing #Vercel #Netlify #GitHub #FrontendArchitecture #SoftwareDesign #CodingSkills #WebTech #TechBlog #Harshal #CodingBestPractices #WebPerformanceTips #JavaScriptBestPractices #ReactTips #UIEngineering

𝗬𝗼𝘂𝗿 𝗰𝗼𝗱𝗲 𝗶𝘀𝗻’𝘁 𝘀𝗺𝗮𝗿𝘁… 𝘂𝗻𝘁𝗶𝗹 𝗶𝘁 𝗰𝗮𝗻 𝗺𝗮𝗸𝗲 𝗱𝗲𝗰𝗶𝘀𝗶𝗼𝗻𝘀. Writing JavaScript isn’t just about functions and variables. It’s about teaching your code 𝘄𝗵𝗲𝗻 𝘁𝗼 𝗱𝗼 𝘄𝗵𝗮𝘁. That’s where Conditional Statements come in 👇 🔹 𝟭. 𝗶𝗳 𝗦𝘁𝗮𝘁𝗲𝗺𝗲𝗻𝘁 👉 Runs code when a condition is true Example: if (age >= 18) { console.log("Eligible to vote"); } ✅ Use case: Basic decision-making 🔹 𝟮. 𝗶𝗳...𝗲𝗹𝘀𝗲 👉 Handles two possible outcomes Example: if (age >= 18) { console.log("Adult"); } else { console.log("Minor"); } ✅ Use case: Binary conditions 🔹 𝟯. 𝗲𝗹𝘀𝗲 𝗶𝗳 𝗟𝗮𝗱𝗱𝗲𝗿 👉 Multiple conditions Example: if (marks >= 90) { console.log("A"); } else if (marks >= 75) { console.log("B"); } else { console.log("C"); } ✅ Use case: Grading systems, multi-level checks 🔹 𝟰. 𝘀𝘄𝗶𝘁𝗰𝗵 𝗦𝘁𝗮𝘁𝗲𝗺𝗲𝗻𝘁 👉 Cleaner alternative for multiple exact matches Example: switch (role) { case "admin": console.log("Full access"); break; case "user": console.log("Limited access"); break; default: console.log("Guest"); } ✅ Use case: Role-based logic, menus 🔹 𝟱. 𝗧𝗲𝗿𝗻𝗮𝗿𝘆 𝗢𝗽𝗲𝗿𝗮𝘁𝗼𝗿 (? :) 👉 Short form of if-else Example: const result = age >= 18 ? "Adult" : "Minor"; ✅ Use case: Clean inline conditions (especially in React) 🔹 𝟲. 𝗟𝗼𝗴𝗶𝗰𝗮𝗹 𝗢𝗽𝗲𝗿𝗮𝘁𝗼𝗿𝘀 𝗶𝗻 𝗖𝗼𝗻𝗱𝗶𝘁𝗶𝗼𝗻𝘀 Example: if (isLoggedIn && isVerified) { console.log("Access granted"); } ✅ Use case: Combining multiple conditions 🔹 𝟳. 𝗡𝘂𝗹𝗹𝗶𝘀𝗵 𝗖𝗼𝗮𝗹𝗲𝘀𝗰𝗶𝗻𝗴 (??) Example: let name = userName ?? "Guest"; ✅ Use case: Default values only when null or undefined 𝗙𝗶𝗻𝗮𝗹 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆 Great developers don’t just write code… They write code that thinks and decides. Which conditional do you use the most in your daily coding? 👇 💡 Part of my #FrontendRevisionMarathon — breaking down frontend concepts daily 🚀 🚀 Follow Shubham Kumar Raj for more such content. #JavaScript #WebDevelopment #Frontend #CodingTips #100DaysOfCode #codinginterview #learnjavascript #programming #interviewprep #CareerGrowth #SowftwareEngineering #OpenToWork #ReactJS #FrontendDevelopment #Coding #Hiring

𝗧𝗼𝗽𝗶𝗰 𝟭𝟮: 𝗘𝘃𝗲𝗻𝘁 𝗟𝗼𝗼𝗽 (𝗠𝗮𝗰𝗿𝗼 𝘃𝘀 𝗠𝗶𝗰𝗿𝗼𝘁𝗮𝘀𝗸𝘀) JavaScript is single-threaded, yet it handles thousands of concurrent operations without breaking a sweat. The secret isn't raw speed; it's an incredibly strict, ruthless prioritization engine. If you don't understand the difference between a macro and a microtask, your "asynchronous" code is a ticking time bomb for UI freezes. Summary: The Event Loop is the conductor of JavaScript's concurrency model. It continuously monitors the Call Stack and the Task Queues. To manage asynchronous work, it uses two distinct queues with vastly different priorities: Macrotasks (like setTimeout, setInterval, network events) and Microtasks (like Promises and MutationObserver). Crux: The VIP Queue: Microtasks have absolute priority. The engine will not move to the next Macrotask, nor will it allow the browser to re-render the screen, until the entire Microtask queue is completely empty. The Normal Queue: Macrotasks execute one by one. After a single Macrotask finishes, the Event Loop checks the Microtask queue again. The Starvation Risk: Because Microtasks can spawn other Microtasks, a recursive Promise chain can hold the main thread hostage, permanently blocking the UI from updating. The Deep Insight (Architect's Perspective): Traffic Control and Yielding: As architects, we must visualize the Event Loop as a traffic control system where Microtasks are emergency vehicles. When you resolve a massive chain of Promises or heavy async/await logic, you are flooding the intersection with ambulances. The browser's rendering engine—the normal traffic—is forced to sit at a red light until every single emergency vehicle has cleared. We don't just use async patterns for code readability; we must actively manage thread occupancy. For heavy client-side computations, we must intentionally interleave Macrotasks (like setTimeout(..., 0)) to force our code to yield control back to the Event Loop, allowing the browser to paint frames and keeping the UI responsive. Tip: If you have to process a massive dataset on the frontend (e.g., parsing a huge JSON file or formatting thousands of rows), do not use Promise.all on the entire set at once. That floods the Microtask queue and locks the UI. Instead, "chunk" the array and process each chunk using setTimeout or requestAnimationFrame. This gives the Event Loop room to breathe and the browser a chance to render 60 frames per second between your computation chunks. Tags: #SoftwareArchitecture #JavaScript #WebPerformance #EventLoop #FrontendEngineering #CleanCode

https://lnkd.in/dA_cAjBs — I used to think I knew React, until I realized I was just writing code that 'worked' but didn't scale. 💡 As a Senior Frontend Engineer, I’ve seen how the definition of a "modern baseline" for TypeScript and React.js has shifted drastically in just the last year. 🔍 I remember a project where we relied on a generic boilerplate that looked great on GitHub. Two months in, the bundle size was a nightmare and the TypeScript types were just 'any' in disguise. 😅 That experience changed how I approach engineering deep-dives. For Part 96 of my React series, I focused on the shifts that actually matter for high-performance apps. ✨ We aren't just looking at basic components anymore. We are talking about leveraging React 19 features alongside Tailwind CSS for maintainable styling. 💎 I spent weeks documenting how to move from messy state logic to clean TanStack Query implementations. 🚀 Plus, why Vite and Storybook have become my non-negotiable duo for rapid prototyping. Testing is another area where people cut corners. I break down how to use Testing Library to ensure your logic actually holds up in the wild. 🛠️ This 5000-word guide is for the developer who is tired of basic tutorials. It’s for the engineer who wants to master the boilerplate React patterns and complex chart js with react integrations used at scale. 📈 What is one React pattern you used to love but now consider an anti-pattern? #FrontendEngineer #TypeScript #ReactJS #WebDevelopment #JavaScript #React19 #TailwindCSS #TanStackQuery #Vite #Storybook #TestingLibrary #SoftwareEngineering #Coding #WebDev #Programming #FrontendEngineers #ReactTips #ReactHooks #TypeScriptTutorial #NextJS #WebPerformance #ModernWeb #SoftwareArchitecture #CodeQuality #DeveloperExperience #FullStack #SoftwareDeveloper #TechCommunity #ReactDeveloper #BoilerplateReact #ChartJS #ReactTestingLibrary #BestReactCourse #ReactComponent #ReactServerComponents #AgGrid #UseState #ReactTutorial #TypeScriptAdvanced #TypeScriptInterview #TSX #ReactNative #ReactTesting #WebDesign #UIUX #CleanCode #ScalableWeb #TechBlog #Harshal #FrontendArchitecture #StateManagement #UnitTesting #ReactPatterns #WebStandard #ES6 #JavaScriptDeveloper #FrontendDevelopment #DevLife #OpenSource #CodingBootcamp #LearnToCode #ProgrammingTips #WebApps #AppDevelopment #SoftwareDesign #WebTech #TechNews #EngineeringExcellence #ComponentLibrary #ResponsiveDesign #FrontendTips #CodeOptimization #JSFrameworks #EnterpriseSoftware #CareerInTech

🚀 Understanding JSX in React — Syntax & Rules Simplified! If you're working with React, JSX is everywhere. But JSX is not HTML—it’s JavaScript with a syntax extension. 💡 What is JSX? JSX (JavaScript XML) lets you write UI like this: const element = <h1>Hello, World!</h1>; 👉 Behind the scenes, React converts this into: React.createElement("h1", null, "Hello, World!"); ⚙️ How JSX works 👉 JSX is compiled into JavaScript 👉 It describes what the UI should look like 👉 React uses it to create Virtual DOM 🧠 Key Rules of JSX (Very Important!) 🔹 1. Return a single parent element // ❌ Wrong return ( <h1>Hello</h1> <p>World</p> ); // ✅ Correct return ( <> <h1>Hello</h1> <p>World</p> </> ); 🔹 2. Use className instead of class <div className="container"></div> 🔹 3. JavaScript inside {} const name = "React"; <h1>Hello {name}</h1> 🔹 4. Self-closing tags <img src="image.png" /> 🔹 5. Inline styles as objects <div style={{ color: "red" }}></div> 🧩 Real-world use cases ✔ Building UI components ✔ Rendering dynamic data ✔ Conditional UI rendering ✔ Mapping lists 🔥 Best Practices (Most developers miss this!) ✅ Keep JSX clean and readable ✅ Extract complex logic outside JSX ✅ Use fragments instead of unnecessary divs ❌ Avoid writing heavy logic inside JSX ⚠️ Common Mistake // ❌ Too much logic inside JSX return <h1>{user.isLoggedIn ? "Welcome" : "Login"}</h1>; 👉 Fine for small cases, but extract logic for complex UI 💬 Pro Insight JSX is not about writing HTML in JS— 👉 It’s about describing UI in a declarative way 📌 Save this post & follow for more deep frontend insights! 📅 Day 6/100 #ReactJS #FrontendDevelopment #JavaScript #JSX #WebDevelopment #SoftwareEngineering #100DaysOfCode 🚀

https://lnkd.in/dVNHkwV2 — If you're a Frontend Engineer, you know the difference between a "working" UI and a "robust" one is often hidden in the TypeScript types. I’ve spent the last few weeks diving into how we bridge the gap between complex CSS layouts and type-safe components. Last year, I broke a production dashboard because of a z-index conflict with a `css fixed` element that wasn't properly typed in our design system 🚀. It was a humbling moment that reminded me why even "basic" CSS properties need a strict architectural approach if you want to scale. To become a top 1% engineer, you can't just copy-paste from Tailwind CSS or shadcn/ui docs without understanding the underlying mechanics 💡. You have to understand how React 19 handles refs and how Next.js 15 optimizes layouts for the modern web. This 5,000-word guide is part 15 of my journey to document every edge case—from `css first of type` selectors to optimizing data fetching with TanStack Query 🛠️. We're moving towards a world where Vite makes builds instant, but our code quality often still lags behind. Real mastery is knowing exactly how `css flex gap` behaves across mobile browsers while maintaining a perfectly clean, type-safe codebase 🏗️. I wrote this for the engineers who aren't satisfied with "it works on my machine" and want to master the craft 📈. Whether you are handling `css margin top` logic or complex state, the goal is the same: Predictability 🎨. Mastering these nuances is what separates the senior talent from the rest of the pack 💻. What's the one CSS property that consistently gives you a headache in TypeScript projects? ✅ Drop your thoughts below! #FrontendEngineer #TypeScript #ReactJS #NextJS #WebDevelopment #Coding #Programming #SoftwareEngineering #CSS #TailwindCSS #JavaScript #Frontend #WebDev #UIUX #SoftwareDeveloper #CleanCode #React19 #NextJS15 #Vite #TanStackQuery #ShadcnUI #WebDesign #DevCommunity #LearnToCode #CodeNewbie #FullStack #TechTrends #SoftwareDevelopment #SeniorEngineer #EngineeringManager #WebPerformance #DesignSystems #ComponentLibrary #OpenSource #GitHub #TechStack #ModernWeb #CodingLife #Programmer #DigitalNomad #RemoteWork #CareerInTech #TechTips #WebStandards #HTML5 #CSS3 #ES6 #PerformanceOptimization #SystemDesign #SoftwareArchitecture #CSSTricks #TypeScriptTips #ReactTips #FrontEndDev #FullStackDeveloper #JuniorDeveloper #MidLevelDeveloper #StaffEngineer #PrincipalEngineer #FrontendEngineers #CodingBestPractices #BuildInPublic #SaaS #SoloFounder #IndieHackers #TechStartup #WebApps #AppDevelopment #ProductEngineering #Debugging #CodeQuality #DeveloperExperience #DX #SoftwareTesting #DevOps

🚀 Closure in JavaScript — Explained Like a Senior React Developer Closures are one of those concepts that look simple… but power some of the most critical patterns in React ⚡ 👉 What is a Closure? A closure is when a function remembers variables from its outer scope, even after the outer function has finished execution. 💡 In short: Function + Lexical Scope = Closure --- 🔹 Basic Example function outer() { let count = 0; return function inner() { count++; console.log(count); }; } const counter = outer(); counter(); // 1 counter(); // 2 👉 Even though outer() is done, inner() still remembers count That’s the power of closure. --- 🔹 Why Closures Matter in React? Closures are everywhere in React: ✔️ Hooks (useState, useEffect) ✔️ Event handlers ✔️ Async operations (setTimeout, API calls) ✔️ Custom hooks --- 🔹 Real-world React Problem: Stale Closure ⚠️ setCount(count + 1); setCount(count + 1); ❌ Both use the same old value of count ✅ Correct approach: setCount(prev => prev + 1); setCount(prev => prev + 1); 👉 This avoids stale closure and ensures latest state is used --- 🔹 Where Closures Help ✅ Data encapsulation (private variables) ✅ Memoization & performance optimization ✅ Debouncing / throttling ✅ Custom hooks ✅ Cleaner state management --- 🔥 Pro Insight (Senior Level) Closures are the backbone of React’s functional paradigm. Misunderstanding them can lead to bugs in: useEffect dependencies Async logic Event callbacks --- 💬 One-line takeaway 👉 “Closures allow functions to retain access to their scope — making React hooks and async logic work seamlessly.” --- #JavaScript #ReactJS #Frontend #WebDevelopment #Programming #InterviewPrep #SoftwareEngineering

#js #10 **What is Execution Context, Call Stack and Call Back Queue in Javascript** 🧠 1. What is Execution Context? 👉 Execution Context = The environment where JavaScript code runs 📦 Types of Execution Context 1. Global Execution Context (GEC)    Created when program starts    Runs global code    let a = 10;    👉 This runs inside Global Execution Context 2. Function Execution Context (FEC) Whenever a function is called: function greet() { console.log("Hello"); } greet(); 👉 A new execution context is created for greet() 🧩 What’s inside Execution Context? Each context has: Memory (Variables) Code (Execution) 🥞 2. What is Call Stack? 👉 Call Stack = A stack where execution contexts are stored and executed Think of it like plates stacked on top of each other 🔄 How Call Stack Works Example: function one() { two(); } function two() { console.log("Hello"); } one(); Step-by-step: Global Execution Context pushed one() called → pushed two() called → pushed console.log runs two() removed one() removed Stack flow: Call Stack: [ Global ] [ one() ] [ two() ] ← runs Then: [ Global ] 📥 3. What is Callback Queue? 👉 Callback Queue = A queue where async callbacks wait before execution Example: console.log("Start"); setTimeout(() => { console.log("Async"); }, 2000); console.log("End"); Flow: Start → runs setTimeout → goes to browser End → runs After 2 sec → callback goes to Callback Queue 🔄 How everything connects Now combine all three: 👉 Call Stack 👉 Callback Queue 👉 Event system → Event Loop 🔁 Final Flow Call Stack runs normal code Async task completes → goes to queue Event loop checks: If stack empty → move task from queue → stack 🧑🍳 Simple Analogy Execution Context = workspace 🧑💻 Call Stack = stack of tasks 📚 Callback Queue = waiting line 🚶 Event Loop = manager checking when to allow next 🎯 Quick Comparison Concept Meaning Execution Context Environment where code runs Call Stack Where functions execute Callback Queue Where async tasks wait 🧾 Final Summary Execution Context = where code runs Call Stack = manages execution order (LIFO) Callback Queue = stores async callbacks Event Loop connects everything 💡 One-line understanding 👉 JavaScript uses execution contexts inside a call stack, and async tasks wait in a callback queue until the event loop pushes them for execution. #Javascript #ObjectOrientedProgramming #SoftwareDevelopment