Rahul Jha’s Post

Most React performance advice is wrong. Not because the patterns are bad but because developers apply them without understanding what React is actually doing. Here’s what I’ve learned: React.memo without useCallback is just theater. memo tells React: “Only re-render if prop references change.” But if you pass a new function reference on every render, memo does absolutely nothing. // ❌ Kills memo on every render <ProductCard onSelect={(id) => handleSelect(id)} /> // ✅ Actually works const handleSelect = useCallback((id) => { dispatch({ type: "SELECT", payload: id }); }, [dispatch]); useMemo has a cost use it surgically. React still performs dependency comparison on every render. For cheap computations, the memoization overhead can be higher than simply recalculating. Use useMemo only when: the computation is genuinely expensive the result is passed to a memoized child you’ve measured it, not assumed it Before reaching for memo or useMemo, ask: What is actually triggering the re-render? Can you eliminate the trigger instead of memoizing around it? Structural state changes beat memoization every time. What’s the nastiest React performance bug you’ve hit in production? #React #ReactJS #Frontend #TypeScript #WebDevelopment #MERN #JavaScript #SoftwareEngineering

🚀 React.memo — Prevent Unnecessary Re-renders Like a Pro In React, re-renders are normal… 👉 But unnecessary re-renders = performance issues That’s where React.memo helps. 💡 What is React.memo? React.memo is a higher-order component (HOC) 👉 It memoizes a component 👉 Prevents re-render if props haven’t changed ⚙️ Basic Example const Child = React.memo(({ name }) => { console.log("Child rendered"); return <h1>{name}</h1>; }); 👉 Now it only re-renders when name changes 🧠 How it works 👉 React compares previous props vs new props If same: ✅ Skips re-render If changed: 🔁 Re-renders component 🔥 The Real Problem Without memo: <Child name="Priyank" /> 👉 Even if parent re-renders 👉 Child also re-renders ❌ With React.memo: ✅ Child re-renders only when needed 🧩 Real-world use cases ✔ Large component trees ✔ Expensive UI rendering ✔ Lists with many items ✔ Components receiving stable props 🔥 Best Practices (Most developers miss this!) ✅ Use with stable props ✅ Combine with useCallback / useMemo ✅ Use in performance-critical components ❌ Don’t wrap every component blindly ⚠️ Common Mistake // ❌ Passing new function each render <Child onClick={() => console.log("Click")} /> 👉 Breaks memoization → causes re-render 💬 Pro Insight (Senior-Level Thinking) 👉 React.memo is not magic 👉 It works only if: Props are stable Reference doesn’t change 📌 Save this post & follow for more deep frontend insights! 📅 Day 21/100 #ReactJS #FrontendDevelopment #JavaScript #PerformanceOptimization #ReactHooks #SoftwareEngineering #100DaysOfCode 🚀

I made React slower trying to optimize it. Wrapped everything in useMemo. Added useCallback everywhere. Felt productive. Performance got worse. Here's what I didn't understand about re-renders 👇 4 things that trigger a re-render: > State change > Prop change > Parent re-renders (even if YOUR props didn't change) > Context update That third one is responsible of unnecessary re-renders I've seen in real codebases. The fix isn't memorizing APIs. It's this order: 1. Profile first Open React DevTools Profiler. Find the actual problem. Takes 2 minutes. 2. Wrap the right components in React.memo Not all of them. Only components that are expensive AND receive stable props. 3. Stabilise your functions with useCallback Without it - new function reference every render --> child always re-renders. Doesn't matter if you have React.memo. 4. useMemo for heavy calculations only Not for "this array map looks expensive." Only when Profiler proves it. The rule I follow now: Don't optimise what you haven't measured. One change in the right place beats 10 changes in the wrong ones. What's the most unnecessary useMemo you've ever written? 😄 #React #JavaScript #Frontend #WebDev

𝗥𝗲𝗮𝗰𝘁 𝗵𝗮𝗱 𝗮 𝗽𝗿𝗼𝗯𝗹𝗲𝗺. It couldn’t pause work. Imagine a chef in a kitchen — One order comes in. He starts cooking. 10 more orders arrive. He ignores them until the first one is done. That was React before v16. One big render started → nothing else could happen. Typing lagged. Animations froze. Users felt it. So the React team asked: What if React could prioritize work? Enter — 𝗥𝗲𝗮𝗰𝘁 𝗙𝗶𝗯𝗲𝗿. 🔥 Fiber is React’s reconciliation engine that enables 𝗶𝗻𝘁𝗲𝗿𝗿𝘂𝗽𝘁𝗶𝗯𝗹𝗲 𝗮𝗻𝗱 𝗽𝗿𝗶𝗼𝗿𝗶𝘁𝗶𝘇𝗲𝗱 𝗿𝗲𝗻𝗱𝗲𝗿𝗶𝗻𝗴. Instead of doing everything at once, React now: ⏸️ Pauses rendering ⚡ Prioritizes urgent updates 🔁 Resumes work seamlessly Think of it like a smart kitchen: VIP order? Done first. Bulk prep? Scheduled. Urgent issue? Everything pauses instantly. This shift unlocked modern React features: → useTransition → Suspense → useDeferredValue → Concurrent rendering React 16 introduced it. React 18 made it powerful. Most developers use React daily… without realizing Fiber is doing the heavy lifting behind the scenes. Once you understand Fiber, you stop writing React — and start thinking like React #React #JavaScript #Frontend #WebDev #ReactFiber

If you think every re-render updates the DOM, this will change your mind. Rendering in React is just a function call. Your component runs, returns JSX, and React calculates what the UI should look like. That’s it. Now the important part 👇 Re-rendering does NOT mean the DOM was updated. It only means 👉 React called your component again The DOM is updated later and only if something actually changed. So the real flow is: Trigger → state or props change Render → React runs your component Commit → React updates only the differences This is why you can type inside an input, the component re-renders, and your text is still there. Because React doesn’t touch what hasn’t changed. The real optimization isn’t avoiding re-renders It’s understanding what happens after them. #React #FrontendDevelopment #JavaScript #WebDevelopment #SoftwareEngineering #ReactJS #FrontendEngineer #TechCareers #CodingTips #DeveloperMindset

For a long time, I tried to stop React from re-rendering. Turns out, I was solving the wrong problem. React is already fast at rendering. The real issue isn’t re-renders—it’s 𝐰𝐡𝐚𝐭 𝐲𝐨𝐮 𝐝𝐨 𝐝𝐮𝐫𝐢𝐧𝐠 𝐞𝐚𝐜𝐡 𝐫𝐞𝐧𝐝𝐞𝐫. If your component runs expensive logic every time it renders, performance will suffer no matter how many optimizations you add. A simple example: const sortedUsers = users.sort((a, b) => a.age - b.age) This runs on every render. A better approach: const sortedUsers = useMemo(  () => users.slice().sort((a, b) => a.age - b.age),  [users] ) Now the sorting only happens when `users` actually change. This small shift changed how I think about performance. The goal is not fewer renders—it’s 𝐥𝐞𝐬𝐬 𝐰𝐨𝐫𝐤 𝐩𝐞𝐫 𝐫𝐞𝐧𝐝𝐞𝐫. Once you focus on that, tools like `useMemo` and `useCallback` start making sense instead of being overused blindly. 💡 Here’s what I apply in real projects: ✔️ Avoid heavy computations directly inside render ✔️ Use `useMemo` only for expensive operations ✔️ Measure before optimizing—don’t guess React performance isn’t about tricks. It’s about understanding where the real cost is. 💬 𝐖𝐡𝐞𝐧 𝐝𝐢𝐝 𝐑𝐞𝐚𝐜𝐭 𝐩𝐞𝐫𝐟𝐨𝐫𝐦𝐚𝐧𝐜𝐞 𝐟𝐢𝐧𝐚𝐥𝐥𝐲 “𝐜𝐥𝐢𝐜𝐤” 𝐟𝐨𝐫 𝐲𝐨𝐮? 👉 Follow Usman Ahmed for more Updates! #ReactJS #FrontendEngineering #WebPerformance #JavaScript #CleanCode #SoftwareEngineering #ReactHooks

🚨 Most developers misunderstand React re-rendering I used to think: 👉 “React re-renders = DOM updates” ❌ Wrong. Here’s what actually happens: 🧠 Rendering = React running your component 🔁 Re-render = React running it again BUT… 👉 React does NOT update the DOM every time Instead: ⚡ It creates a Virtual DOM ⚡ Compares old vs new (Reconciliation) ⚡ Updates ONLY what changed 💥 Real insight: 👉 The real problem is NOT DOM updates 👉 It’s unnecessary re-renders Example: Parent re-renders → Child also re-renders Even when nothing changed ❌ 🛠️ Fix: 🛡️ React.memo → skip child render if props same 📦 useMemo → keep props stable Together: 👉 Stable props + memoized component = no wasted work 🧠 Biggest learning today: 👉 “React doesn’t repaint everything… it only fixes what changed.” #React #Frontend #WebDevelopment #Performance #JavaScript #OpenSource

React Fiber: what it actually means for your code Most React devs know what Fiber is by name. Fewer know why it matters day to day. The old reconciler worked synchronously. State changes, React walks the whole tree, diffs it, writes to the DOM. One pass, no stopping. On a large component tree that blocked the main thread long enough for users to notice — animations stuttered, inputs lagged. Fiber fixed this by replacing the recursive call stack with a linked list. Each fiber is a plain object: component type, props, state, and pointers to parent, first child, next sibling. React now owns the execution, so it can pause whenever something more urgent comes in. Work splits into two phases, and this is the part worth understanding. The render phase builds a work-in-progress tree in memory without touching the DOM. React can stop mid-tree, hand control back to the browser for a keypress or a frame, then continue. If a higher-priority update arrives, it discards the in-progress work and starts over. The commit phase doesn't pause. Once the tree is ready, React applies all DOM mutations in one go. This part has to be synchronous — a half-applied DOM update breaks the UI. Here's where it connects to your actual code. useTransition works because React can genuinely deprioritize a state update and interrupt it if needed. Without Fiber, marking something as "non-urgent" would be meaningless — the old reconciler couldn't stop anyway. Suspense pauses a subtree while data loads for the same reason. React keeps the current tree on screen, builds the new one in the background, swaps when ready. Slow renders that only appear under load, inputs that lag when a big list re-renders, Suspense boundaries not behaving as expected — all of these trace back to how Fiber schedules and interrupts work. When something's off and the profiler gives you a confusing flamegraph, knowing that React works in two phases (one interruptible, one not) usually tells you where to look. #react #frontend #javascript #webdev #reactjs #frontenddevelopment #softwaredevelopment

There’s something interesting about working with Next.js in real-world projects — the benefits don’t always show up in documentation, but they become obvious once things go into production. One noticeable shift is how performance starts improving without constant manual optimization. Features like Server Components quietly reduce client-side load, which reflects directly in smoother user interactions. Routing and layouts also feel more structured. Instead of managing scattered logic, the project naturally moves toward a cleaner architecture, especially as it scales. Another practical observation is with Incremental Static Regeneration (ISR). It helps keep content fresh without sacrificing speed — something that used to require custom solutions before. On the development side, iteration feels faster. Changes reflect quickly, debugging becomes simpler, and overall friction reduces during builds. But the real difference shows up in consistency — fewer performance issues, better load times, and a more stable user experience over time. Next.js doesn’t feel like just another framework in the stack anymore. It starts influencing how applications are designed from the ground up. Curious — what changes have you noticed after using Next.js in actual projects? #NextJS #FrontendDevelopment #WebPerformance #JavaScript #TechInsights

🚀 Day 32/100 – #100DaysOfCode Today I’m sharing another React project: 🔗 Book Vibe – Book Discovery Platform This project is focused on creating a clean and interactive platform for exploring books and reading-related content. 🔹 Project Idea The main goal is to build a system where users can browse, explore, and interact with books in a structured and user-friendly way. 🔹 Core Features - Display books dynamically from data - Explore book details (title, author, etc.) - Smooth navigation between pages - Responsive and clean UI 🔹 Core Concepts Used - Dynamic Data Rendering → Showing book data using .map() - Routing & Navigation → Moving between pages without reload - State Management → Handling user interactions and UI updates - Component-Based Design → Breaking UI into reusable parts - Recharts → Beautiful visual chart activity 🔹 What This Project Demonstrates - How to build a content-based application - Managing and displaying structured data - Creating a smooth user experience with React Live Link: https://lnkd.in/gYxJsuT4 Don't forget to share your thoughts in the comments below! 32 days down, 68 more to go.| | #Day32 #100DaysOfCode #ReactJS #WebDevelopment #FrontendDevelopment #JavaScript #Projects