React App Slow: Misusing useMemo and React.memo

🚀React Bundle Analysis & Optimization Your React app might look fine… But if your bundle is heavy, users will feel the slowdown ⚠️ Let’s break this down simply 👇 🧩 What is a Bundle? 👉 When you build a React app, all your code + libraries are combined into JavaScript files (bundles) 💡 Example: • React • UI libraries • Utility functions ➡️ All packed into one or multiple JS files ⚠️ Why Large Bundles Are a Problem ❌ Slow initial load ❌ More JavaScript to execute ❌ Poor performance on low-end devices 👉 Bigger bundle = Slower app 🔍 What is Bundle Analysis? 👉 It helps you understand: • Which library is heavy • What is increasing bundle size • Where optimization is needed 📊 Tools give a visual breakdown of your bundle 🛠️ Tools You Can Use ✔ webpack-bundle-analyzer ✔ source-map-explorer 👉 Shows which dependency is taking the most space ⚡ How to Optimize Bundle 🧩 1. Code Splitting → Break bundle into smaller chunks ⚡ 2. Lazy Loading → Load components only when needed 🌳 3. Tree Shaking → Remove unused code automatically 📦 4. Dynamic Imports → Load heavy modules on demand 🧹 5. Remove Heavy Libraries → Replace with lighter alternatives 🔥 Real Impact ✔ Faster load time ✔ Better performance ✔ Improved user experience ✔ Smaller bundle size 🧠 Simple Way to Understand • Without Optimization → Big bundle → Slow app ❌ • With Optimization → Small chunks → Fast app ✅ 💬 Have you ever checked what’s inside your bundle? #React #WebPerformance #Frontend #JavaScript #WebDevelopment #Optimization #Coding #SoftwareEngineering

🚀 Day 22/30 – Folder Structure (Scalable React Apps) Most React projects don’t fail because of code… 👉 They fail because of bad structure 😵 Today I learned how real-world React apps are structured ⚡ 👉 Folder Structure (Industry Level) 💻 The Problem: Everything works fine… until your app grows 👀 ❌ Files everywhere ❌ Hard to find logic ❌ Debugging becomes painful 💻 The Solution: 👉 Feature-based architecture (used in production) ✅ 📁 Example Structure: src/ ┣ app/ → app setup (store, providers) ┣ features/ → business logic (modular) ┃ ┣ auth/ ┃ ┃ ┣ components/ ┃ ┃ ┣ pages/ ┃ ┃ ┣ services/ ┃ ┃ ┣ hooks/ ┃ ┃ ┗ authSlice.js ┃ ┣ user/ ┃ ┗ product/ ┣ shared/ → reusable code ┃ ┣ components/ ┃ ┣ hooks/ ┃ ┣ utils/ ┃ ┗ constants/ ┣ services/ → API config ┣ routes/ → routing ┣ layouts/ → layouts ┣ assets/ → images ┣ App.jsx ┗ main.jsx 💡 Why this is powerful: ✅ Each feature is isolated ✅ Easy to scale without chaos ✅ Teams can work independently 🔥 Reality Check: 👉 Small apps → basic structure works 👉 Real apps → need architecture ⚡ Advanced Insight: Most beginners organize by file type ❌ Real developers organize by feature/domain ✅ 🔥 Key Takeaway: Clean architecture > clean code Be honest 👇 Are you still using basic folders… or building scalable apps? 🚀 #React #FrontendDevelopment #JavaScript #CleanCode #Architecture

🚀 Code Splitting in React — Best Practices & Why It Matters Ever noticed your React app taking time to load? 🤔 That’s often because everything loads at once… 👉 This is where Code Splitting comes in ⚡ 🧩 What is Code Splitting? 👉 Break your app into smaller chunks 👉 Load only what’s needed Instead of loading the entire app at once, React loads components on demand 💡 ⚙️ Basic Example js import React, { Suspense, lazy } from "react"; const Dashboard = lazy(() => import("./Dashboard")); export default function App() { return ( <Suspense fallback={<p>Loading...</p>}> <Dashboard /> </Suspense> ); } 🧠 Best Practices ✔ Use `React.lazy()` for components ✔ Wrap with `Suspense` for fallback UI ✔ Split routes (page-level splitting) ✔ Avoid over-splitting (too many small chunks) ✔ Combine with dynamic imports ⚡ Why It Matters? ✔ Faster initial load time ✔ Better performance ✔ Improved user experience ✔ Reduced bundle size 🔥 Real-world Usage 👉 Large dashboards 👉 E-commerce apps 👉 Admin panels 👉 Feature-based modules 🧠 Simple Way to Understand • Without Code Splitting → Load everything 🚫 • With Code Splitting → Load only needed parts ✅ 💬 Are you using code splitting in your project or still loading everything at once? --- #React #Frontend #WebPerformance #JavaScript #WebDevelopment #Coding #SoftwareEngineering

🚀 𝗗𝗲𝗰𝗼𝗱𝗲 𝗠𝗘𝗥𝗡 𝘄𝗶𝘁𝗵 𝗠𝗲 – 𝗗𝗮𝘆 𝟳 Today’s focus wasn’t just UI… It was about writing smarter React code. I explored 𝗖𝘂𝘀𝘁𝗼𝗺 𝗛𝗼𝗼𝗸𝘀— a concept that changes how you structure your applications. Instead of repeating logic in multiple components, I learned how to extract it into a reusable function. So I built a simple project to apply it 👇 📌 𝗣𝗿𝗼𝗷𝗲𝗰𝘁: Notes App with Auto Save A minimal app, but with a strong concept behind it. ✔ Notes are saved automatically ✔ Data persists even after refresh ✔ No backend used — everything handled in the browser ✔ Clean and simple UI with Tailwind CSS ⚙️ 𝗪𝗵𝗮𝘁 𝗺𝗮𝗱𝗲 𝗶𝘁 𝗶𝗻𝘁𝗲𝗿𝗲𝘀𝘁𝗶𝗻𝗴? I created a custom hook: useLocalStorage This hook handles: • State management • Data storage • Sync between UI and localStorage One hook → reusable logic → cleaner components 🧠 𝗞𝗲𝘆 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆: When your logic is reusable, your code becomes scalable. And that’s where React starts to feel powerful. 🔗 𝗖𝗼𝗱𝗲: https://lnkd.in/gBuMk4TG Learning one concept at a time. Building one project at a time. #MERN #ReactJS #CustomHooks #WebDevelopment #LearningInPublic #100DaysOfCode

Nobody talks about this React performance trap — and it bit me hard in production. I was using useContext to manage auth + theme + cart state in a mid-size app. Only a few components actually used the cart state. But every time the cart updated — every single component consuming the context re-rendered. Even the ones that only needed the user's name. Here's why: React's Context API re-renders all consumers whenever the context value reference changes — regardless of which slice of state they actually use. There are workarounds with Context: → Split into multiple contexts (AuthContext, CartContext, ThemeContext separately) → Wrap consumers in React.memo() → Use useMemo to stabilize the context value But honestly? All of these feel like duct tape. This is exactly where Zustand and Redux Toolkit shine. Both let you subscribe to only the slice of state you need. A component using useSelector(state => state.user.name) will only re-render when that specific value changes — not when the cart updates, not when the theme toggles. ZUSTAND Minimal boilerplate, great for small-to-mid apps. Selector-based subscriptions built in. REDUX TOOLKIT Structured, scalable. useSelector memoizes out of the box with Reselect. The lesson I took away: useContext is great for low-frequency, global state (auth, theme, locale). The moment you have state that changes often and is consumed by many components — reach for a proper state manager. Performance issues in React are rarely obvious until they're in production. Knowing why re-renders happen matters more than memorizing which hook to use. Have you run into this? Would love to hear how you solved it — Context splitting, Zustand, RTK, or something else entirely? #ReactJS #JavaScript #WebDevelopment #Frontend #Zustand #Redux

Here’s something that took me a while to accept… You can build a Next.js app that works perfectly fine. Pages load, data shows up, and users can click around. And yet, you could still be doing it completely wrong. Not wrong in a "this will crash" way. Wrong in a quieter way... The kind of wrong that results in 800 KB JavaScript bundles for a simple landing page. The kind of wrong that creates hidden data waterfalls, making your app feel sluggish despite being "modern." I’ve seen this in countless code reviews. I’ve seen it in projects from senior React devs. And I definitely did it myself. The issue isn’t skill. It’s a mental model problem. Next.js forces you to make decisions that React never asked you to make: Does this component live on the server or the client? Should this data be cached, revalidated, or fetched fresh? Is this a Server Action or an API route? Does it even matter? Spoiler: It’s the difference between a secure app and a data leak. In standard React, everything runs in the browser. In Next.js, every decision changes the architecture of your entire app. Get them wrong, and the app still "works," it just doesn't work the way Next.js was engineered to work. Most developers don’t realize they’re building a "React app inside a Next.js folder" until it’s too late to change. #NextJS #ReactJS #FrontendDevelopment #SoftwareEngineering #JavaScript #FullStackDevelopment #SystemDesign #WebPerformance #CleanCode #BuildInPublic #DeveloperExperience #AppArchitecture

Your React app feels slow, and you have no idea why. The truth is, it is probably re-rendering 10x more than it should be. React core philosophy is that UI is a function of state. When state changes, React re-evaluates the component tree. But if you are not careful, a single state change at the top of your tree can trigger a massive wave of unnecessary re-renders all the way down to the bottom. Here are the 3 most common reasons your React app is re-rendering too much: 1. Passing new object references in props. If you pass an inline object or function like style={{ color: 'red' }} or onClick={() => doSomething()}, React sees a brand new reference on every single render. Even if the contents are identical, React thinks the prop changed. 2. State lifted too high. If you have a form input that updates on every keystroke, and its state lives in a parent component alongside heavy data tables, typing one letter re-renders the entire table. 3. Missing memoization. Complex calculations or heavy child components that do not depend on the changed state will still re-render by default. React is fast, but it is not magic. Example: Instead of passing inline functions like this: <Button onClick={() => handleSubmit()} /> Use useCallback to keep the reference stable: const handleSubmit = useCallback(() => { ... }, []); <Button onClick={handleSubmit} /> Key takeaways: - Keep state as close to where it is used as possible. - Use memo for expensive child components. - Use useMemo and useCallback to preserve reference equality for objects and functions passed as props. #reactjs #webdevelopment #frontend #javascript #performance #softwareengineering #coding #webdev #reactdeveloper #programming

Your React app isn't slow. Your folder structure is just a mess. When a React project grows, the "group by file type" approach breaks down. Putting all components in one folder, hooks in another, and utils somewhere else is a recipe for disaster. You end up scrolling through hundreds of files just to fix one bug. Here is how you structure a large React project for scale. Stop grouping by file type. Start grouping by feature. A feature-based architecture means everything related to a specific part of your app lives together. If you are working on the authentication flow, you should not have to leave the auth folder. Inside your src directory, structure it like this: src/  features/   auth/    components/    hooks/    services/    auth.slice.ts    index.ts  shared/   components/    Button.tsx   hooks/    useClickOutside.ts   utils/    formatDate.ts  app/   store.ts   router.tsx Why this works better: 1. High Cohesion Everything a feature needs is in one place. No more jumping between 5 different directories to understand a single workflow. 2. Strict Boundaries Features should not reach into other features' internals. Use an index.ts file to explicitly export only what is necessary. 3. Easier Onboarding New developers can look at the features folder and immediately understand what the application actually does. When a feature gets too complex, it naturally splits into smaller features. This scales infinitely better than the traditional flat structure. #reactjs #javascript #webdevelopment #frontend #softwareengineering #coding #architecture #cleancode #webdev #reactdeveloper

If removing every useMemo and useCallback from your app changes nothing… They were never fixing the problem. 😭 We’ve all done it. App feels slow → immediately add: useMemo(...) useCallback(...) Suddenly we feel like we’ve optimized the app. 🤡 Meanwhile the real problem is still there: • Rendering 5,000 rows • Fetching 2MB of JSON • Re-rendering the whole page • 14 charts fighting for their lives useMemo and useCallback are useful — but only when they solve an actual bottleneck. If deleting them makes no noticeable difference, they were probably just performance-flavored decoration. And since memoization is not free, you may have actually made things slightly slower. 💀 One exception: If a function is passed as a dependency, useCallback can keep the reference stable. But if the function is only used inside the effect, just move it into the effect: // ❌ Unnecessary const fetchData = useCallback(() => fetch('/api/data'), []); useEffect(() => { fetchData(); }, [fetchData]); // ✅ Simpler useEffect(() => { const fetchData = () => fetch('/api/data'); fetchData(); }, []); Most React apps are not slow because of this: onClick={() => setOpen(true)} They are slow because somewhere deep in the codebase there is a component rendering the entire internet on every keystroke. 😭 React’s advice is simple: Profile first. Then optimize. Otherwise you are just making the code harder to read for free. We didn’t optimize the app. We put Flex Tape on a waterfall. 🌊 #ReactJS #JavaScript #WebDev #Frontend #ReactHooks #FrontendDevelopment #SoftwareEngineering #DevHumor #CodeNewbie #100DaysOfCode

🚀 Is Your React App Slowing Down? It Might Be Your Bundle Size One silent performance killer in React apps is a large JavaScript bundle. The bigger your bundle, the longer it takes to: Load ⏳ Parse 🧠 Execute ⚙️ And users? They feel it immediately. 💡 The Fix: Code Splitting + Lazy Loading Instead of shipping your entire app at once… 👉 Load only what the user needs, when they need it. 🧩 Code Splitting Break your app into smaller chunks. Each route or feature becomes its own bundle instead of one massive file. ⚡ Lazy Loading with React.lazy Load components on demand: const CityList = React.lazy(() => import("./CityList")); 🎯 Use with Suspense <Suspense fallback={<Spinner />}> <CityList /> </Suspense> 👉 Now your component loads only when needed, not upfront. 🛣️ Route-Based Splitting (Best Practice) Perfect for pages: const Home = React.lazy(() => import("./pages/Home")); const Product = React.lazy(() => import("./pages/Product")); Users only download the page they visit 👇 Not your entire app. 🔥 Why This Matters ✅ Faster initial load time ✅ Better performance on low-end devices ✅ Improved user experience ✅ Lower data usage 🧠 Pro Tip Don’t lazy load everything. 👉 Lazy load: Pages Heavy components (charts, maps, editors) 👉 Don’t lazy load: Small reusable components (buttons, inputs) 🧩 Final Thought Performance isn’t just about writing code… It’s about when your code loads. Ship less. Load smarter. Scale better. #React #WebPerformance #Frontend #JavaScript #CodeSplitting #LazyLoading #SoftwareEngineering