React Key Prop Importance in Lists

🚀 Day 5/30 – State in React One of the most important concepts 🔥 Today I learned: ✅ State stores dynamic data inside a component → It allows components to manage and update their own data ✅ When state changes → React re-renders the UI → React automatically updates only the changed parts (efficient rendering ⚡) ✅ Managed using useState hook → The most commonly used hook in functional components ✅ State updates are asynchronous → React batches updates for better performance 💻 Example: import { useState } from "react"; function Counter() { const [count, setCount] = useState(0); const handleClick = () => { setCount(prev => prev + 1); // safe update }; return ( <div> <h2>Count: {count}</h2> <button onClick={handleClick}>Increment</button> </div> ); } 🔥 Key Takeaway: State is what makes React components interactive, dynamic, and responsive to user actions. #React #State #FrontendDevelopment #JavaScript #WebDev #CodingJourney #LearnInPublic

🚨 I used index as key in React… …and spent HOURS debugging something that made no sense. Everything looked fine at first. Until I: → deleted an item → reordered the list 💥 Suddenly: ❌ Wrong data was displayed ❌ UI behaved randomly ❌ Bugs I couldn’t explain I kept checking my logic. Turns out… the bug wasn’t my logic. 👉 It was THIS: {data.map((item, index) => ( <div key={index}>{item.name}</div> ))}💡 Problem: React uses keys to track identity. When you use index: → identity = position ❌ → not the actual item So when the list changes… React gets confused 😵 ✅ Fix: {data.map((item) => ( <div key={item.id}>{item.name}</div> ))}👉 Stable key = stable UI 💡 Lesson: If your UI feels “random”… check your keys before your logic. Follow me for more such tips ✍️ 👨💻 #ReactJS #Frontend #JavaScript #SoftwareEngineering

🚀 React State Management — Learned Today! Built a dynamic product list in React where users can add new items through a form — and the UI updates instantly! ⚡ What I implemented: ✅ Controlled components with useState ✅ Props drilling — passing functions from parent to child ✅ Spreading state to add new objects in array ✅ Form handling with e.preventDefault() Key lesson learned: Always pass state variable (newitem) to child components — not the static array (item) — otherwise UI won't re-render! 🧠 jsx setNewitem([...newitem, { name: data.title, date: new Date(data.date) }]); Slowly but steadily building my React fundamentals! 💪 🔗 GitHub: https://lnkd.in/g_7SwfZm #React #JavaScript #MERN #WebDevelopment #100DaysOfCode #Frontend #AccioJob

Topic: Stale Closures in React – The Hidden Bug You Don’t See Coming ⚠️ Stale Closures in React – The Bug That Looks Fine… Until It’s Not Your code works. No errors. No warnings. But suddenly… state behaves incorrectly 😐 Welcome to the world of stale closures. 🔹 What is a Stale Closure? When a function captures an old value of state instead of the latest one. 🔹 The Problem const [count, setCount] = useState(0); useEffect(() => { const interval = setInterval(() => { console.log(count); // ❌ always logs old value }, 1000); return () => clearInterval(interval); }, []); 👉 count is stuck at its initial value. 🔹 Why This Happens React closures capture values at render time, not at execution time. 🔹 Solutions ✅ 1. Add dependency useEffect(() => { console.log(count); }, [count]); ✅ 2. Use functional update setCount(prev => prev + 1); ✅ 3. Use useRef for latest value const countRef = useRef(count); countRef.current = count; 💡 Real-World Impact 👉 Timers 👉 WebSockets 👉 Event listeners 👉 Async callbacks 📌 Golden Rule If your logic depends on changing state, make sure it’s not using a stale snapshot. 📸 Daily React tips & visuals: 👉 https://lnkd.in/g7QgUPWX 💬 Have you ever debugged a stale closure issue for hours? 😅 #React #ReactJS #JavaScript #FrontendDevelopment #WebDevelopment #ReactHooks #DeveloperLife

🚀 Today I Learned: Different Ways to Handle Forms in React Today I explored multiple ways to handle forms in React, and it helped me understand the difference between Controlled and Uncontrolled Components. 🔹 Controlled Components In this approach, form data is handled by React state. Every input change updates the state using onChange, which makes React the single source of truth. ✅ Better control over form data ✅ Easy validation and dynamic behavior 🔹 Uncontrolled Components Here, form data is handled by the DOM itself instead of React state. We usually use refs to access the input values when needed. ✅ Less code for simple forms ✅ Useful when you don't need real-time state updates 💡 Learning both approaches made me realize that choosing the right method depends on the complexity of the form and the level of control needed. Every day I dive deeper into React fundamentals, and understanding concepts like these makes building real applications much easier. #React #WebDevelopment #JavaScript #FrontendDevelopment #LearningInPublic

React Re-rendering Is NOT What You Think… When I started React, I thought: “State changes → Component re-renders → Done” Simple… right? But I was completely WRONG Truth: React doesn’t just re-render that one variable It re-renders the ENTIRE component Example: const [count, setCount] = useState(0); console.log("Component Rendered"); Every click → Whole component runs again All functions re-created All calculations re-execute The Mistake I Made: I was doing heavy work inside components like: const filteredData = data.filter(...) So every render → Expensive calculations again Performance drop The Fix (Game Changer): useMemo() const filteredData = useMemo(() => { return data.filter(...) }, [data]); -----Now it only runs when needed Another Hidden Issue: Functions inside components const handleClick = () => {} Re-created on EVERY render Fix? useCallback() Golden Rule: If something is: Expensive → useMemo Function passed to child → useCallback My Learning: React is not about writing code It’s about controlling re-renders What about you? Did you know your whole component re-renders every time? Devendra Dhote Daneshwar Verma Ritik Rajput #reactjs #javascript #webdevelopment #frontend #performance #coding #reactdeveloper #learninpublic

🔥 Why useEffect Runs Twice in React Strict Mode If you’ve seen this while developing with React: JSX code : useEffect(() => { console.log("Effect ran"); }, []); You expect this to run once. But in development, the console shows: Effect ran Effect ran So… is React broken? Not really. 🧠 What’s Actually Happening When React Strict Mode is enabled, React intentionally runs some lifecycle logic twice in development. This includes useEffect. Why? Because React is checking if your effects are safe and predictable. 🔍 What React Is Testing React wants to detect bugs like: Side effects that are not cleaned up Code that relies on running only once Hidden memory leaks To do that, React: 1️⃣ Mounts the component 2️⃣ Runs the effect 3️⃣ Immediately unmounts it 4️⃣ Mounts it again If your cleanup logic is correct, everything still works. ✅ Example with Cleanup JSX code useEffect(() => { const id = setInterval(() => { console.log("running"); }, 1000); return () => clearInterval(id); }, []); This ensures no leftover side effects. 🎯 Important Note This only happens in development. Production builds run effects normally. #ReactJS #FrontendDevelopment #JavaScript #ReactHooks #WebDevelopment #LearningInPublic

Lazy Loading in React, Boost Performance Like a Pro! Lazy loading is a powerful technique in React where components are loaded only when they are needed, instead of loading everything at once. 👉 Think of it as: Lazy Loading = Code Splitting = Dynamic Imports = On-demand Loading 💡 Why use Lazy Loading? ✔️ Improves performance ✔️ Reduces initial bundle size ✔️ Faster page load experience 🛠️ Key Methods - React.lazy() - for dynamic imports - Suspense - for fallback UI (like loaders) 📌 Basic Syntax const Component = React.lazy(() => import('./Component')); <Suspense fallback={<h1>Loading...</h1>}> <Component /> </Suspense> ⚙️ How it works - Components load only when required - A fallback UI is shown until loading completes 📍 Common Use Cases - Routing (React Router) - Large components - Dashboards ⚠️ Important Points - Works with default exports only - Must be wrapped inside Suspense - It’s a key part of code splitting 🔥 If you are aiming for scalable and high-performance React apps, lazy loading is a must-know concept! #ReactJS #JavaScript #WebDevelopment #FrontendDevelopment #CodeSplitting #PerformanceOptimization #ReactDeveloper #Programming #TechTips #SoftwareDevelopment

I built a Todo App using HTML, CSS, and JavaScript to practice core frontend development concepts. Through this project I worked with: 1. DOM manipulation 2. Event listeners 3. Array methods like map() and filter() 4. LocalStorage for data persistence Features currently implemented: • Add tasks • Mark tasks as completed • Delete tasks • Clear completed tasks • Remaining tasks counter Next step: implementing task filtering (All / Active / Completed). Always learning and building 🚀 Live Demo: https://lnkd.in/g6eQ8yFa GitHub Repo: https://lnkd.in/gzF9ZNHX #WebDevelopment #JavaScript #FrontendDeveloper #CodingJourney

⚛️ Improving React Performance with Lazy Loading As React applications grow, the bundle size can increase significantly. Loading all components at once can slow down the initial page load and impact the user experience. React Lazy Loading helps solve this problem by loading components only when they are needed, instead of including everything in the main JavaScript bundle. With tools like "React.lazy()" and "Suspense", React can split the code and dynamically load components when a user navigates to them. Benefits of React Lazy Loading: • Smaller initial bundle size • Faster page load • Better performance on slower networks • Improved overall user experience Optimizing how and when components load is a key step in building scalable and high-performance React applications. Reference from 👉 Sheryians Coding School #React #WebDevelopment #Frontend #JavaScript #Performance #SoftwareEngineering