React useEffect dependency issues silently hurting performance

🧠 React Doesn’t Update State Immediately (Even Inside the Same Function) Most people know state is async. But here’s the part many don’t realize 👇 Example const [count, setCount] = useState(0); function handleClick() { setCount(count + 1); if (count === 0) { console.log("Still zero?"); } } You click the button. Expected: count = 1 But inside that function… 👉 count is still 0 🔍 Why? Because React doesn’t update state inside the current render cycle. It schedules the update and re-renders later. 🧠 The tricky part Even this won’t work: setCount(count + 1); setCount(count + 1); 👉 Final result = +1, not +2 ✅ Correct way setCount(prev => prev + 1); setCount(prev => prev + 1); Now React uses the latest value. 🎯 The Real Insight State inside a function is a snapshot, not a live value. 💥 Why this matters This causes: Unexpected conditions Wrong calculations Confusing bugs #ReactJS #FrontendDevelopment #JavaScript #ReactHooks #WebDevelopment #CodingTips #LearningInPublic

Avoid Unnecessary Re-renders in React Many React applications become slow not because of bad logic, but because of unnecessary re-renders. To understand this better, I prepared a short PDF explaining: -Memoization in React -useMemo vs useCallback vs React.memo -When optimization is useful -When memoization actually makes performance worse -Best practices for real projects Always remember: Measure first, optimize later. Sharing this guide for developers who want to improve React performance. #ReactJS #FrontendDeveloper #CleanCode #PerformanceOptimization #JavaScript

💡Class components Vs Functional Components💡 As you might know, starting with React version 16.8.0, React hooks are introduced. So starting with version 16.8.0, you can have state and lifecycle methods in functional components which were not possible before in functional components. Today, you can achieve almost everything using react hooks(functional components) that you can do in class components. But there are still 3 lifecycle methods available in class components for which there is no equivalent react hook. These lifecycle methods are: ✅ getSnapshotBeforeUpdate ✅ getDerivedStateFromError ✅ componentDidCatch So If you want to use these lifecycle methods, then you need to use the class components instead of react hooks(functional components). 𝗙𝗼𝗿 𝗺𝗼𝗿𝗲 𝘀𝘂𝗰𝗵 𝘂𝘀𝗲𝗳𝘂𝗹 𝗰𝗼𝗻𝘁𝗲𝗻𝘁, 𝗱𝗼𝗻'𝘁 𝗳𝗼𝗿𝗴𝗲𝘁 𝘁𝗼 𝗳𝗼𝗹𝗹𝗼𝘄 𝗺𝗲. #javascript #reactjs #nextjs #webdevelopment

react 19 has a new use() api and it breaks one of the oldest rules in react hooks must be called at the top level. always. no conditions, no loops. use() doesn't care. you can call it inside if statements, loops, conditionals - things that were never allowed before. it does two things: - reads a promise (integrates with suspense automatically) - reads context (like useContext, but more flexible) function UserCard({ userPromise }) { const user = use(userPromise); // suspends until resolved return <p>{user.name}</p>; } the catch? create your promises in server components and pass them down - not inside the client component itself, or you'll get an infinite loop on every re-render. it's a small api with a big mental shift. react is clearly moving toward a world where async is first-class - not something you bolt on with useEffect + useState + loading flags. #react #react19 #frontend #javascript #webdev

I just deleted 30 lines of code from a React component. no refactor. no library. just one hook in React 19. it's called use() — and it changes how you handle async data and context in your components. most devs haven't heard of it yet. swipe through ↓ broke it down simply what's the most boilerplate you've deleted in a single React upgrade? 👇 #react #react19 #javascript #webdev #frontend

💡 Today I learned something that changed how I think about performance in React… I was working on a simple search input, and everything seemed fine… until I realized something Every single keystroke was triggering an API call That means: 👉 Too many requests 👉 Unnecessary load on the server 👉 A less smooth user experience That’s when I remembered 𝗱𝗲𝗯𝗼𝘂𝗻𝗰𝗶𝗻𝗴 Instead of calling the API on every key press, I added a small delay. Now, the function only runs when the user stops typing for a moment ✨ The result? Fewer API calls Better performance Cleaner and more efficient code Sometimes, it’s not about big changes… but small improvements that make a real difference Have you ever faced this kind of issue? 👇 #React #WebDevelopment #JavaScript #Frontend #Performance #LearningJourney

One React topic that gets messy fast: forms. Not because inputs are hard. Because real-world forms are. Validation, async errors, dynamic fields, reusable logic: that’s where clean React patterns matter. I broke it down here 👇 https://lnkd.in/dFWB3Phc #reactjs #frontenddevelopment #javascript #webdevelopment #softwareengineering #buildinpublic

One of the biggest mistakes I made early in React: 👉 Overusing useEffect. After working with React for 3 years, I realized: Most useEffect usage is unnecessary. Here’s when you should NOT use useEffect 👇 ❌ 1. Deriving state from props If you can calculate it directly during render, don’t store it in state. Bad: const [fullName, setFullName] = useState("") useEffect(() => { setFullName(firstName + " " + lastName) }, [firstName, lastName]) Better: const fullName = firstName + " " + lastName ❌ 2. Handling simple calculations React re-renders already — no need for effects. ❌ 3. Updating state based on another state This often leads to unnecessary re-renders or bugs. ✅ When should you use useEffect? API calls Subscriptions (e.g., WebSocket) DOM side effects 💡 Rule I follow now: “If it can be calculated during render, don’t use useEffect.” This one shift made my code: ✔ Simpler ✔ Easier to debug ✔ More performant React is powerful — but only when used correctly. What’s one mistake you used to make in React? #React #FrontendDevelopment #JavaScript #CleanCode #WebDev

Topic: React Batching – Why Multiple setState Calls Don’t Always Re-render ⚡ React Batching – Multiple setState Calls, One Render (But Not Always) Ever written this and expected 2 re-renders? 👇 setCount(c => c + 1); setCount(c => c + 1); But React only re-renders once 🤯 Why? 👉 Batching 🔹 What is Batching? React groups multiple state updates and processes them in a single render cycle. 🔹 Why It Matters ✔ Better performance ✔ Fewer unnecessary renders ✔ Smoother UI updates 🔹 Before React 18 😓 Batching worked only in: 👉 Event handlers Not in: ❌ setTimeout ❌ Promises 🔹 After React 18+ 🚀 Automatic batching works almost everywhere: ✔ setTimeout ✔ async/await ✔ API calls 🔹 Example setTimeout(() => { setA(1); setB(2); }); 👉 Still only one render in modern React 💡 Important Note If you need immediate update: flushSync(() => setCount(1)); 📌 Golden Rule React tries to do more work in fewer renders. 💬 Did batching ever confuse you while debugging state updates? #React #ReactJS #StateManagement #FrontendDevelopment #JavaScript #WebDevelopment #DeveloperLife

💡 𝗧𝗶𝗽 𝗼𝗳 𝘁𝗵𝗲 𝗗𝗮𝘆 — 𝗥𝗲𝗮𝗰𝘁 𝗗𝗶𝗱 𝘆𝗼𝘂 𝗸𝗻𝗼𝘄? In React, 𝗲𝘃𝗲𝗻𝘁 𝗵𝗮𝗻𝗱𝗹𝗲𝗿𝘀 𝗿𝗲𝗰𝗲𝗶𝘃𝗲 𝗮 𝘀𝘆𝗻𝘁𝗵𝗲𝘁𝗶𝗰 𝗲𝘃𝗲𝗻𝘁, 𝗻𝗼𝘁 𝘁𝗵𝗲 𝗻𝗮𝘁𝗶𝘃𝗲 𝗯𝗿𝗼𝘄𝘀𝗲𝗿 𝗲𝘃𝗲𝗻𝘁. React wraps native events in a 𝗦𝘆𝗻𝘁𝗵𝗲𝘁𝗶𝗰𝗘𝘃𝗲𝗻𝘁 to ensure consistent behavior across browsers. 🔧 𝗪𝗵𝘆 𝘁𝗵𝗶𝘀 𝗺𝗮𝘁𝘁𝗲𝗿𝘀: - You get a unified API regardless of the browser - But the event object may be 𝗽𝗼𝗼𝗹𝗲𝗱 𝗮𝗻𝗱 𝗿𝗲𝘂𝘀𝗲𝗱 𝗕𝗲𝘀𝘁 𝗽𝗿𝗮𝗰𝘁𝗶𝗰𝗲: If you need to access the event asynchronously, store needed values immediately. Understanding this helps avoid subtle bugs. #React #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #SoftwareEngineering #CodingTips #BestPractices #FullstackDeveloper