React Native Questions

The React Native Bridge acts as an intermediary between the JavaScript thread and the Native (iOS/Android) threads.

• JavaScript code runs on the JS thread.
• Native code (Objective-C/Java) runs on the Native thread.
• They communicate asynchronously by passing JSON messages over the Bridge.

Real Interview Experience - Aptara (React Native Role) Question: We have a FlatList rendering 5000 items with images. It's lagging. How do you fix it?

My Answer / Approach:

1. Use initialNumToRender to limit initial render items (e.g., 10).
2. Use windowSize to limit the memory consumed by items outside the viewport.
3. Use removeClippedSubviews={true} to unmount off-screen components.
4. Use getItemLayout to skip measurement calculations if items have a fixed height.
5. Memoize the renderItem component using React.memo to prevent unnecessary re-renders.
6. Use FastImage (react-native-fast-image) instead of the default Image component for better caching.