Using React.memo and useMemo helps your React Native app avoid unnecessary re-rendering. This keeps the frame rate smooth, aiming for 60fps or higher, which means animations and interactions feel fast and natural. Without these, your app might waste CPU and memory on components that don't need to update, causing janky scrolling or slow UI responses. Efficient memoization also reduces battery drain by lowering CPU usage.
Use React.memo to wrap functional components that receive props but don't always need to update. This tells React to skip re-rendering if props haven't changed. Use useMemo to memoize expensive calculations or objects so they don't get recreated on every render. Avoid overusing these hooks; only memoize when you see performance issues or when components are heavy. Profiling with React DevTools helps identify where memoization is beneficial.
Both React.memo and useMemo are built-in React APIs and add no extra bundle size. They do not increase startup time. Their impact is purely on runtime performance by reducing unnecessary work. Using them wisely can improve perceived app speed without affecting app size.
React Native uses the same React APIs on both iOS and Android, so React.memo and useMemo behave identically across platforms. However, performance gains might feel different due to device hardware and OS optimizations. Android devices vary more in CPU power, so memoization can have a bigger impact on lower-end devices. iOS devices tend to have more consistent performance, but memoization still helps maintain smooth UI.
Neither Apple App Store nor Google Play Store have specific rules about using React.memo or useMemo. However, both stores require apps to be responsive and not freeze or crash. Efficient rendering helps meet these requirements by preventing UI hangs. Also, avoid excessive memory use or battery drain, which can cause app rejection. Using memoization correctly supports these guidelines by improving app stability and user experience.
If your screen is slow to load, it might be because components are re-rendering too often or expensive calculations run on every render. Check if you are missing React.memo on components that receive unchanged props or if you need useMemo to cache heavy computations. Also, verify that you are not creating new objects or functions inline that cause re-renders. Profiling with React DevTools can help find these issues.