Artem Krasovskyi’s Post

🚀 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 🚀

Have you ever needed to touch the DOM directly while working in React? React is designed to be declarative. You describe the UI based on state, and the library handles the updates. But occasionally, you need what we call an 'escape hatch.' This is precisely where 'refs' come into play. They provide a way to access a DOM node or a React element directly, bypassing the standard re-render cycle. The most common reason to reach for a ref is to manage things like focus, text selection, or media playback. If you need a specific input field to focus the moment a page loads, you cannot easily do that with state alone. You need to reach into the DOM and call the native '.focus()' method. Beyond the DOM, refs are also perfect for storing any mutable value that needs to persist across renders without triggering a UI update. This includes things like timer IDs or tracking previous state values for comparison. However, with great power comes responsibility. Using refs is essentially stepping outside of the React ecosystem and taking manual control. If you can achieve your goal using props and state, you should. Overusing refs can make your components harder to debug and breaks the predictable flow of data that makes React so reliable. It is a tool for the edge cases, not the daily routine. Use it when you need to talk to the browser directly, but keep your core logic declarative. #ReactJS #SoftwareEngineering #WebDevelopment #Javascript #Frontend #CodingTips

You wrapped your component in React.memo… but it still re-renders 🤔 I ran into this more times than I’d like to admit. Everything looks correct. You’re using React.memo. Props don’t seem to change. But the component still re-renders on every parent update. Here’s a simple example: const List = React.memo(({ items }) => { console.log('List render'); return items.map(item => ( <div key={item.id}>{item.name}</div> )); }); function App() { const [count, setCount] = React.useState(0); const items = [{ id: 1, name: 'A' }]; return ( <> <button onClick={() => setCount(count + 1)}> Click </button> <List items={items} /> </> ); } When you click the button the List still re-renders. At first glance, it feels wrong. The data didn’t change… so why did React re-render? The reason is subtle but important: every render creates a new array. So even though the content is the same, the reference is different. [] !== [] And React.memo only does a shallow comparison. So from React’s perspective, the prop did change. One simple fix: const items = React.useMemo(() => [ { id: 1, name: 'A' } ], []); Now the reference stays stable and memoization actually works. Takeaway React.memo is not magic. It only helps if the props you pass are stable. If you create new objects or functions on every render, you’re effectively disabling it without realizing it. This is one of those bugs that doesn’t throw errors… but quietly hurts performance. Have you ever debugged something like this? 👀 #reactjs #javascript #frontend #webdevelopment #performance #reactperformance #softwareengineering #programming #coding #webdev #react #typescript

Most frontend developers are still writing raw Intersection Observer code by hand. It works but it adds boilerplate, cleanup logic, and SSR concerns that distract from the actual problem. There is a React hook that handles all of this quietly in the background: useInView from react-intersection-observer. It is one of the most practical hooks in the React ecosystem and, in my experience, one of the least talked about. WHAT IT SOLVES Lazy loading images and components only when they enter the viewport Triggering scroll-based animations without fighting useEffect and useRef Firing analytics events when a section becomes visible Building infinite scroll without a third-party pagination library Auto-playing media only when it is actually in view WHY IT DOES NOT GET ENOUGH ATTENTION Most learning resources teach Intersection Observer from the ground up, which builds understanding but rarely translates into production-ready patterns. This hook is the practical layer on top of that knowledge. It handles unmount cleanup, root margin configuration, SSR-safe behavior, and one-time trigger support things that developers typically spend time rediscovering on their own. The next time a design requirement involves scroll-triggered behavior, reach for this before writing the observer setup manually. What patterns are you using it for? Would be glad to hear how others are applying it. #React #Frontend #WebDevelopment #JavaScript #ReactHooks

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

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

Your component is re-rendered... Then what? Most developers stop thinking here. And that’s where the real magic starts. This is Post 3 of the series: 𝗥𝗲𝗮𝗰𝘁 𝗨𝗻𝗱𝗲𝗿 𝘁𝗵𝗲 𝗛𝗼𝗼𝗱 Where I explain what React is actually doing behind the scenes. React does NOT update the DOM immediately. Because touching the DOM is expensive. Instead, it follows a 3-step process: Render → Diff → Commit First, React creates something called a 𝗩𝗶𝗿𝘁𝘂𝗮𝗹 𝗗𝗢𝗠. Not the real DOM. Just a JavaScript object in memory. A blueprint of your UI. Every time your component runs, React builds a new tree of this Virtual DOM. And it already has the previous tree stored. Now comes the interesting part. React compares: Old tree vs New tree This step is called 𝗗𝗶𝗳𝗳𝗶𝗻𝗴. It finds exactly what changed. Not everything. Just the difference. Then comes the final step: 𝗖𝗼𝗺𝗺𝗶𝘁 phase React takes only those changes… …and updates the real browser DOM So no, React is NOT re-rendering your whole page. It’s doing surgical updates. The key insight: React separates thinking from doing. Thinking = Render + Diff Doing = Commit That’s why React is fast. Because touching the DOM is expensive. So React minimizes it. Flow looks like this: ✅️ Component runs ✅️ Virtual DOM created ✅️ Changes calculated ✅️ DOM updated ✅️ Browser paints UI Once you see this, you stop fearing re-renders. And start understanding them. In Post 4 of React Under the Hood: How does React actually compare trees? (The diffing algorithm 👀) Follow Farhaan Shaikh if you want to understand react more deeply. 👉 Read in detail here: https://lnkd.in/dTYAbM6n #React #Frontend #WebDevelopment #JavaScript #SoftwareEngineering

Most React performance problems don’t come from re-renders. They come from creating new identities every render. This is something I completely overlooked for years. --- Example 👇 const options = { headers: { Authorization: token } }; useEffect(() => { fetchData(options); }, [options]); Looks harmless. But this runs on every render. Why? Because "options" is a new object every time → new reference → dependency changes → effect runs again. --- Now imagine this in a real app: - API calls firing multiple times - WebSocket reconnecting randomly - Expensive logic running again and again All because of reference inequality, not value change. --- The fix is simple, but rarely discussed 👇 const options = useMemo(() => ({ headers: { Authorization: token } }), [token]); Now the reference is stable. The effect runs only when it should. --- This doesn’t just apply to objects: - Functions → recreated every render - Arrays → new reference every time - Inline props → can break memoization --- The deeper lesson: React doesn’t compare values. It compares references. --- Since I understood this, my debugging approach changed completely. Whenever something runs “unexpectedly”, I ask: 👉 “Did the reference change?” --- This is one of those small concepts… that silently causes big production issues. --- Curious — have you ever debugged something like this? #ReactJS #Frontend #JavaScript #WebDevelopment #Performance

💡 Understanding a subtle React concept: Hydration & “bailout” behavior One interesting nuance in React (especially with SSR frameworks like Next.js) is how hydration interacts with state updates. 👉 Hydration is the process where React makes server-rendered HTML interactive by attaching event listeners and syncing state on the client. When a page is server-rendered, the initial HTML is already in place. During hydration, React attaches event listeners and syncs the client state with that UI. Here’s the catch 👇 👉 If the client-side state matches what React expects, it may skip updating the DOM entirely. This is due to React’s internal optimization often referred to as a “bailout”. 🔍 Why this matters In cases like theme handling (dark/light mode): If the server renders a default UI (say light mode ☀️) And the client immediately initializes state to dark mode 🌙 React may still skip the DOM update if it doesn’t detect a meaningful state transition 👉 Result: UI can temporarily reflect the server version instead of the actual state. 🧠 Conceptual takeaway A more reliable pattern is: ✔️ Start with an SSR-safe default (consistent with server output) ✔️ Then update state after hydration (e.g., in a layout effect) This ensures React sees a real state change and updates the UI accordingly. 🙌 Why this is fascinating It highlights how deeply optimized React is — sometimes so optimized that understanding its internal behavior becomes essential for building predictable UI. Grateful to the developer community for continuously sharing such insights that go beyond surface-level coding. 🚀 Key idea In SSR apps, correctness isn’t just about what state you set — it’s also about when React observes the change. #ReactJS #NextJS #FrontendDevelopment #WebDevelopment #JavaScript #Learning