Debugging React Timing Issues

I struggled with this React concept more than I expected… 👇 👉 Why are my API calls running twice? ⚙️ What you’ll notice You open your network tab and suddenly see this: api/me → called twice api/roles → called twice api/permissions → called twice Just like in the screenshot 👇 Same request, duplicated… again and again. ⚙️ What’s actually happening In React (development mode), if your app is wrapped in Strict Mode, React will run effects twice on purpose. useEffect(() => { fetch("/api/users") .then(res => res.json()) .then(setUsers); }, []); Even though it looks like it should run once… it doesn’t (in dev). 🧠 What’s going on under the hood React basically does a quick cycle: mount → unmount → remount Why? To catch hidden side effects To check if cleanup is handled properly To make sure your logic doesn’t break on re-renders So if your API call runs twice, React is just making sure your code can handle it. 💡 The important part This only happens in development Production behaves normally (runs once) Your side effects should be safe to run multiple times 🚀 Final thought If your network tab looks “noisy” like the screenshot, it’s not React being broken — it’s React being careful. And once you understand this, debugging becomes a lot less confusing. #React #Frontend #JavaScript #WebDevelopment #ReactJS #SoftwareEngineering

🚀 React Re-rendering — Key Concepts Re-rendering is the core of how React keeps UI in sync with data. Without it, there would be no interactivity in our applications. Here are some important insights I've learned: 🔹 State updates are the primary trigger for re-renders 🔹 When a component re-renders, all its child components re-render by default 🔹 Even without props, components still re-render during the normal render cycle (without use of memoization). 🔹 Updating state in a hook triggers a re-render, even if that state isn’t directly used 🔹 In chained hooks, any state update will re-render the component using the top-level hook 🔹 “Moving state down” is a powerful pattern to reduce unnecessary re-renders in large applications #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #SoftwareEngineering #LearningInPublic

There's a page in the React docs called "You Might Not Need an Effect." I'd say it's one of the most important pages in the entire React documentation. And most developers have either never read it or read it once and moved on. The whole idea comes down to one question: is your code syncing React with something React doesn't control? A WebSocket, a browser API, a third-party library? If yes, useEffect makes sense. If no, you're probably just adding extra renders and making your code harder to follow. Some patterns worth knowing: If you're deriving a value from props or state, just calculate it during render. No state, no effect needed. If you're responding to a user action like a click or form submit, put it in the event handler. The event handler already knows what happened. The effect doesn't. If you need to reset state when a prop changes, use the key prop. React will remount the component and reset everything automatically. If you're chaining effects where one sets state and triggers another, collapse all of it into a single event handler. React batches those updates into one render. If a child is fetching data just to pass it up to a parent, flip the flow. Let the parent fetch and pass it down. The rule the docs give is honestly the clearest way I've seen it put: if something runs because the user did something, it belongs in an event handler. If it runs because the component appeared on screen, it belongs in an effect. Every unnecessary useEffect is an extra render pass, an extra place for bugs to hide, and more code for the next person to untangle. Worth a read if you haven't: https://lnkd.in/gqUr7e_S How many effects in your current codebase do you think would actually pass that test? #ReactJS #Frontend #JavaScript #WebDevelopment #CleanCode

🔯 You can finally delete <Context.Provider> 👇 For years, the Context API introduced a small but persistent redundancy. We defined a Context object, yet we couldn't render it directly-we had to access the.Provider property every single time. 🔯 React 19 removes this requirement. ❌ The Old Way: UserContext.Provider It often felt like an implementation detail leaking into JSX. Forget Provider, and your app might silently fail or behave unexpectedly. ✅ The Modern Way: <UserContext> The Context object itself is now a valid React component. Just render it directly. Why this matters ❓ 📉 Less Noise - Cleaner JSX, especially with deeply nested providers 🧠 More Intuitive - Matches how we think: "wrap this in UserContext" 💡Note: Note: <Context.Consumer> is also largely dead in favor of the use hook or useContext. Starting in React 19, you can render <SomeContext> as a provider. In older versions of React, use <SomeContext.Provider>. 💬 Have you tried this in your project? 💬 React 18 or 19 — what are you using? 🔗 Learn More: React Context Docs: https://lnkd.in/dbVWdc-C #React #JavaScript #WebDevelopment #Frontend #React19 #ModernReact #ReactHook #CodingLife #DeveloperJourney #SoftwareDeveloper

🚀 Controlled vs Uncontrolled Components in React — Real-World Perspective Most developers learn: 👉 Controlled = React state 👉 Uncontrolled = DOM refs But in real applications… 👉 The choice impacts performance, scalability, and maintainability. 💡 Quick Recap 🔹 Controlled Components: Managed by React state Re-render on every input change 🔹 Uncontrolled Components: Managed by the DOM Accessed via refs ⚙️ The Real Problem In large forms: ❌ Controlled inputs → Too many re-renders ❌ Uncontrolled inputs → Hard to validate & manage 👉 So which one should you use? 🧠 Real-world Decision Rule 👉 Use Controlled when: ✔ You need validation ✔ UI depends on input ✔ Dynamic form logic exists 👉 Use Uncontrolled when: ✔ Performance is critical ✔ Minimal validation needed ✔ Simple forms 🔥 Performance Insight Controlled input: <input value={name} onChange={(e) => setName(e.target.value)} /> 👉 Re-renders on every keystroke Uncontrolled input: <input ref={inputRef} /> 👉 No re-render → better performance ⚠️ Advanced Problem (Most devs miss this) 👉 Large forms with 20+ fields Controlled approach: ❌ Can slow down typing 👉 Solution: ✔ Hybrid approach ✔ Use libraries (React Hook Form) 🧩 Industry Pattern Modern apps often use: 👉 Controlled logic + Uncontrolled inputs internally Example: ✔ React Hook Form ✔ Formik (optimized patterns) 🔥 Best Practices ✅ Use controlled for logic-heavy forms ✅ Use uncontrolled for performance-critical inputs ✅ Consider form libraries for scalability ❌ Don’t blindly use controlled everywhere 💬 Pro Insight (Senior Thinking) 👉 This is not about “which is better” 👉 It’s about choosing the right tool for the problem 📌 Save this post & follow for more deep frontend insights! 📅 Day 17/100 #ReactJS #FrontendDevelopment #JavaScript #ReactHooks #PerformanceOptimization #SoftwareEngineering #100DaysOfCode 🚀

26 questions. The difference between knowing React on paper and surviving a real production codebase. Here are the 26 questions categorized by the depth of experience required: Level 1: The Foundations => How does React’s rendering process work? => What’s the difference between state and props? => What are hooks, and why were they introduced? => What are controlled vs uncontrolled components? => When would you use refs? => How do you handle forms and validations? Level 2: State & Logic => When should you lift state up? => How do you manage complex state in an application? => When would you use useState vs useReducer? => How do useEffect dependencies work? => How do you handle API calls (loading, error, success states)? => How do you manage shared state across components? => Context API vs Redux — when would you use each? Level 3: Performance & Scale => What causes unnecessary re-renders, and how do you prevent them? => What is memoization in React? => When would you use React.memo, useMemo, and useCallback? => How do you structure a scalable React application? => How do you optimize performance in large-scale apps? => What tools do you use to debug performance issues? => How do you secure a React application? => How do you test React components effectively? Level 4: The War Stories => Have you faced an infinite re-render issue? How did you fix it? => Tell me about a complex UI you built recently. => How did you improve performance in a React app? => What’s the hardest bug you’ve fixed in React? => How do you handle 50+ inputs in a single form without lag? Syntax is easy to Google. Deep understanding is hard to fake. #ReactJS #FrontendDevelopment #TechInterviews #JavaScript #WebDevelopment #Developers

Nobody told me this when I started React. I used it for over a year without really getting it. I could build things. Components, hooks, state — all of it. But something was always slightly off. Like, I was constantly fighting the framework instead of working with it. I'd update the state and then immediately try to read it. I'd wonder why my UI wasn't reflecting what I just changed. I'd add more useEffects, trying to force things to sync. More code. More confusion. Then I came across three characters that broke it all open for me. UI = f(state) That's it. React has one rule. Your UI is not something you control directly — it's the output of a function. You give it your data. It gives you back what the screen should look like. You don't say "update this element." You say, "here's the data." React handles the screen. I know that sounds simple. But I genuinely wasn't thinking this way. I was still mentally treating React like jQuery — find the element, change it, done. That mental model works fine for jQuery. In React it fights you every step. The moment I stopped thinking about updating UI and started thinking about describing UI — everything got easier. My components got smaller. My bugs got fewer. My useEffects stopped multiplying. Because I finally understood: my only job is to get the state right. React's job is everything else. #React #JavaScript #Frontend #ReactJS #WebDevelopment #Programming #100DaysOfCode #SoftwareDevelopment

🚀 Understanding useEffect in React — Simplified! If you're working with React, mastering useEffect is not optional— 👉 It controls how your app interacts with the outside world. 💡 What is useEffect? useEffect is a hook that lets you perform side effects in components. 👉 Side effects include: API calls Event listeners Timers DOM updates ⚙️ Basic Syntax useEffect(() => { // side effect logic }, [dependencies]); 🧠 How it works 1️⃣ Runs after component renders 2️⃣ Re-runs when dependencies change 3️⃣ Cleanup runs before next effect or unmount 🔹 Example useEffect(() => { console.log("Component mounted or updated"); }, []); 👉 Runs only once (on mount) 🔹 With Dependency useEffect(() => { console.log("Count changed"); }, [count]); 👉 Runs when count changes 🔹 Cleanup Function useEffect(() => { const timer = setInterval(() => { console.log("Running..."); }, 1000); return () => clearInterval(timer); }, []); 👉 Prevents memory leaks 🧩 Real-world use cases ✔ Fetching API data ✔ Subscribing to events ✔ Setting intervals / timeouts ✔ Syncing with external systems 🔥 Best Practices (Most developers miss this!) ✅ Always use dependency array correctly ✅ Cleanup side effects properly ✅ Split multiple effects into separate useEffects ❌ Don’t ignore dependencies (can cause bugs) ❌ Don’t overuse useEffect unnecessarily ⚠️ Common Mistake useEffect(() => { fetchData(); }, []); 👉 If fetchData depends on props/state → can cause bugs 💬 Pro Insight useEffect is not just about running code— 👉 It’s about syncing your component with external systems 📌 Save this post & follow for more deep frontend insights! 📅 Day 13/100 #ReactJS #FrontendDevelopment #JavaScript #ReactHooks #useEffect #WebDevelopment #SoftwareEngineering #100DaysOfCode 🚀

𝐈𝐬 𝐑𝐞𝐚𝐜𝐭 𝐚 𝐟𝐫𝐚𝐦𝐞𝐰𝐨𝐫𝐤 𝐨𝐫 𝐚 𝐥𝐢𝐛𝐫𝐚𝐫𝐲? I used to genuinely not know the answer to this. I kept hearing both and just... went along with it. Until I actually looked it up. First stop - the official React docs at https://react.dev. Right there on the homepage it calls itself "the library for web and native user interfaces." Then I checked MDN https://lnkd.in/gTP_zAW4, which is basically the bible for web developers. Same answer - React is a library, not a framework. They even say it outright: "React is not a framework." So what's the actual difference? React only handles the UI layer. That's it. No routing built in, no state management system, nothing like that. You pull in other tools for those things yourself. A framework would give you all of that out of the box - think structure vs. flexibility. That's why React feels like a framework when you're using it in a big project. But technically, it's not. Honestly, once that clicked, the way I think about frontend tools completely changed. I stopped treating React like it was supposed to do everything and started understanding why we add libraries like React Router or Zustand alongside it. Sometimes the confusion isn't about how hard something is - it's just that nobody explained the basics clearly enough from the start. #React #FrontendDevelopment #JavaScript #WebDevelopment #LearningInPublic

🚀 useReducer in React — When useState is Not Enough As your React app grows… 👉 State becomes complex 👉 Multiple updates depend on each other 👉 Logic gets messy That’s where useReducer comes in. 💡 What is useReducer? useReducer is a hook for managing complex state logic using a reducer function. 👉 Inspired by Redux ⚙️ Basic Syntax const [state, dispatch] = useReducer(reducer, initialState); 🧠 How it works 👉 Instead of updating state directly: setCount(count + 1); 👉 You dispatch actions: dispatch({ type: "increment" }); 👉 Reducer decides how state changes: function reducer(state, action) { switch (action.type) { case "increment": return { count: state.count + 1 }; default: return state; } } 🧩 Real-world use cases ✔ Complex forms ✔ Multiple related states ✔ State transitions (loading → success → error) ✔ Large components with heavy logic 🔥 Why useReducer? 👉 useState works well for simple state 👉 useReducer works better for structured logic 🔥 Best Practices (Most developers miss this!) ✅ Use when state depends on previous state ✅ Use for complex or grouped state ✅ Keep reducer pure (no side effects) ❌ Don’t use for simple state ❌ Don’t mix business logic inside components ⚠️ Common Mistake // ❌ Side effects inside reducer function reducer(state, action) { fetchData(); // ❌ Wrong return state; } 👉 Reducers must be pure functions 💬 Pro Insight (Senior-Level Thinking) 👉 useState = simple updates 👉 useReducer = predictable state transitions 👉 If your state has “rules” → useReducer 📌 Save this post & follow for more deep frontend insights! 📅 Day 20/100 #ReactJS #FrontendDevelopment #JavaScript #ReactHooks #StateManagement #SoftwareEngineering #100DaysOfCode 🚀