Apr 14
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React StrictMode Double Rendering Explained React 18 introduced a change that confused a lot of developers: 👉 useEffect runs twice in development. At first, it looks like a bug. But it’s actually a feature designed to catch real production issues. ⸻ What’s Actually Happening In StrictMode (development only): • React mounts the component • Runs the effect • Immediately unmounts it • Then mounts it again This simulates real-world scenarios where: • Components mount/unmount quickly • Users navigate away mid-request • Async operations complete after unmount ⸻ The Problem It Exposes Race condition: • You fetch data • User navigates away • Component unmounts • Fetch completes • setState runs on unmounted component ❌ This leads to: • Memory leaks • Unexpected bugs • Console warnings • Hard-to-debug issues Key Insight React running effects twice is not the problem. Your missing cleanup is. ⸻ When Does This Happen? • Only in development • Only with StrictMode enabled • Does NOT happen in production react useeffect twice, react strict mode explained, react 18 useeffect double render, react cleanup function useeffect, react memory leak fix, react async useeffect, react race condition fix, react hooks tutorial, react 18 changes, react best practices, frontend performance react, react debugging tips #reactjs #reactdeveloper #frontenddevelopment #javascript #webdevelopment #codingtips #programming #reacthooks #useeffect #developer #softwareengineering