Dan Neciu’s Post

🚀 React Evolution : Class Components→Function Components React has come a long way! This illustration perfectly explains why Function Components + Hooks are now the preferred approach. 🔁 Old Way – Class Components - Multiple lifecycle methods ➡️ constructor ➡️ componentDidMount ➡️ componentDidUpdate ➡️ componentWillUnmount - Too many steps to manage state and side effects - More boilerplate, harder to maintain ✅ New Way – Function Components ➡️ One powerful hook: useEffect ➡️ Handles mounting, updating, and cleanup in one place ➡️ Cleaner syntax ➡️ Easier to read, test, and maintain ➡️ Better performance and developer experience 🧠 Think of it as: Many switches ➜ One smart button If you’re still using class components, now is the best time to start migrating and embracing modern React 🚀 #ReactJS #JavaScript #WebDevelopment #FrontendDevelopment #ReactHooks #useEffect #CleanCode #SoftwareEngineering #UIDevelopment #ModernReact #LearningReact

Why can’t we create a state variable outside the component function? const [count, setCount] = React.useState(0); ❌ function Counter() { return <div>{count}</div>; } function Counter() { const [count, setCount] = React.useState(0); ✅ return <div>{count}</div>; } Why? Because Hooks rely on the component’s render cycle. When React renders a component, it: 1️⃣ Calls the component function 2️⃣ Tracks the order of Hooks 3️⃣ Stores state internally based on that order Hooks are tightly connected to the component’s lifecycle. If you declare state outside: ❌ There is no render context ❌ No component lifecycle ❌ React can’t track it #ReactJS #ReactHooks #ReactInternals #FrontendDevelopment #JavaScript #SoftwareEngineering #WebDevelopment #LearningInPublic #ReactInterview #FrontendEngineer #TechInterview

Today I learned how useEffect cleanup actually works in React — and it completely changed how I think about side effects. When we use useEffect, it runs after render. But what many beginners ignore is the cleanup function. Why is cleanup important? Prevents memory leaks Stops unnecessary API calls Removes event listeners properly Clears intervals and timeouts Example: When you add an event listener inside useEffect, you must remove it when the component unmounts. Otherwise, it keeps running in the background. That’s where cleanup comes in. useEffect(() => { const handleResize = () => console.log("Resized"); window.addEventListener("resize", handleResize); return () => { window.removeEventListener("resize", handleResize); }; }, []); The function returned inside useEffect runs: Before the next effect runs When the component unmounts Small detail. Big difference in performance. React is simple — until you understand the details. #ReactJS #FrontendDeveloper #JavaScript #WebDevelopment #LearningInPublic #100DaysOfCode

🚨 Stop using useEffect for everything in React. If you're still using useEffect to: • Derive state from props • Transform data for rendering • Handle simple computations You're probably writing more bugs than you think. 💡 React tip: 1️⃣ Derived data belongs in useMemo, not useEffect 2️⃣ Event-driven logic belongs in handlers 3️⃣ Effects are for synchronization with external systems The less useEffect you write, the more predictable your component becomes. Clean React code is about eliminating unnecessary effects. What’s one place you removed useEffect and simplified your code? #ReactJS #FrontendDevelopment #JavaScript #SoftwareEngineering #CleanCode

🚀 React Re-renders Why does a component re-render even when props look the same? React re-renders when reference changes, not value. If you pass new objects/functions every render, React treats them as new. Example: Passing `{ user }` where `user` is recreated each render will trigger child updates. In dashboards with 100+ rows, this causes lag. Fix: Memoize values and avoid inline object creation. #ReactJS #FrontendEngineering #JavaScript

While starting to learn React, I decided to keep things simple. I built the same Todo List twice with the same UI design: First using pure JavaScript, Then rebuilding it with React. This helped me clearly see the difference between: • JavaScript DOM manipulation • React’s component-based thinking Project features: • Add new tasks • Delete tasks • Toggle task completion • Search tasks • Filter tasks (All / Completed / Not Completed) Small project, but a big learning step for me. Live Demo: JS version: https://lnkd.in/ebWQRNar React version: https://lnkd.in/eJt2Svj7 #React #JavaScript #FrontendDevelopment #WebDevelopment #LearningInPublic #TodoApp

🚀 React+Typescript Practice: Random User Card with Loading State Today I worked on a small React practice project where I: ✅ Fetched data from Random User API ✅ Implemented loading state inside the card UI ✅ Handled conditional rendering properly ✅ Followed correct key usage in map() ✅ Added a refresh button with disabled state during loading This helped me reinforce important React concepts like: useState & useEffect Async/Await data fetching Clean component structure UI-friendly loading handling Small practices like these really help in writing production-ready UI code 💡 Always learning, always improving 🚀 Demo Link- https://lnkd.in/gMQczeKB #ReactJS #FrontendDevelopment #UIDeveloper #JavaScript #WebDevelopment #LearningByDoing

React Hooks: Where Things Often Go Wrong React hooks are powerful, but many issues I see in codebases don’t come from React itself — they come from how hooks are used. A few patterns that usually cause trouble: • useEffect treated like a lifecycle replacement Not everything belongs in an effect. A lot of logic fits better in event handlers or during render. • Dependency arrays that grow endlessly When an effect depends on “everything,” it’s often a sign that responsibilities aren’t clear. • Effects that shouldn’t exist at all Some effects are only compensating for poor state placement or derived state. • Custom hooks that hide complexity Abstraction is useful, but hiding side effects inside hooks can make bugs harder to trace. • useRef used only for DOM access Refs are also great for storing mutable values that shouldn’t trigger re-renders. My takeaway: Hooks don’t replace good component design. Clear ownership of state and responsibilities makes hooks simpler — and bugs rarer ⚛️ #ReactJS #FrontendEngineering #Hooks #WebDevelopment #JavaScript #EngineeringInsights

In React, a Hook is just a JavaScript object. Each Hook stores: the state value a queue of updates and a reference to the next Hook Internally it looks like this: { memoizedState: state, queue: updates, next: nextHook } React stores Hooks as a linked list attached to the component's Fiber node. Fiber → Hook → Hook → Hook → null This is why Hooks must always be called in the same order. React reads them one by one during every render. When you call setState, React adds the update to the Hook's queue, and processes it during the next render. Hooks are not magic. They are simple objects connected together. Understanding this helps explain many React behaviors. #reactjs #javascript #webdevelopment

REACT NOTES — PART 1 (Foundations) After understanding how JavaScript works, the next step is building interfaces that scale. React simplifies complex UIs by breaking them into small, reusable components. This post covers the core foundations: • Components and component structure • JSX and how React renders UI • Virtual DOM and efficient updates • Props for passing data • State for dynamic UI behavior • Event handling in React Before learning advanced patterns or frameworks, these fundamentals must be clear. 📌 Save this if you're starting with React or revising the basics. #React #FrontendDeveloper #WebDevelopment #JavaScript #InterviewPrep #LearningInPublic #Consistency