Most commonly asked interview question in react native

React Native is a widely-used framework for developing cross-platform mobile applications but achieving optimal performance can be challenging. In this blog, we’ll explore key techniques to optimize your React Native application for speed, responsiveness, and efficiency.

Optimizing performance in React Native is a crucial skill that many companies seek during interviews. recently asked this question in these companies like upGrad, Infosys, GlobalLogic, Terrapay, Razorpay, and Capgemini often inquire about performance optimization and best practices.

Why Optimize React Native Apps?

Performance optimization ensures:

Smooth user experience with minimal delays and seamless animations.
Efficient resource utilization to optimize battery life and memory usage.
Scalability to manage growing app complexity effectively.

1. Optimize Rendering

Avoid Unnecessary Re-Renders

Use useMemo and useCallback:
- Cache values and functions to avoid recalculating on every render.
- React.memo: Use this for functional components to prevent re-rendering unless props change.

2. Optimize Lists

Use FlatList or SectionList: These are optimized for rendering large datasets efficiently with lazy loading and virtualization.
Enable Key Extractor: Always provide a unique keyExtractor to FlatList to avoid unnecessary re-renders.
Use getItemLayout: Helps FlatList calculate item positions faster.

  <FlatList 
    data={items} 
    renderItem={({ item }) => <Text>{item.age}</Text>} 
    keyExtractor={(item) => item.id.toString()} 
  />

3. Optimize Images

Resize Images: Use pre-optimized image sizes to avoid resizing on the client.

Use Image Caching: Libraries like react-native-fast-image provide caching and optimized loading.

  import FastImage from 'react-native-fast-image';

  <FastImage 
    source={{ uri: 'https://example.com/image.png' }} 
    style={{ width: 100, height: 100 }} 
  />;

4. Reduce JavaScript Overhead

Minimize Bridge Usage: Limit the amount of data passed between the JavaScript and native threads to reduce latency.
Batch State Updates: Group multiple setState calls to avoid extra renders.
```
  setState((prev) => ({ ...prev, key1: value1, key2: value2 }));
```
Debounce Heavy Computations: Use debounce or throttle to limit frequent calls in event handlers like scroll or text input.

  import { debounce } from 'lodash';

  const handleReduce = debounce((txt) => {
    setSearchText(txt);
  }, 500);

5. Monitor Performance

Enable Debugging Tools: Use tools like React DevTools, Flipper, and the built-in profiler to monitor performance.
Log Slow Renders: Use the onRender callback to log slow components.

6. Memory Management

Avoid Memory Leaks:

Unsubscribe from listeners in the useEffect cleanup.
Clear timeouts or intervals in componentWillUnmount.

useEffect(() => {
  const interval = setInterval(() => {}, 1000);
  return () => clearInterval(interval); // Cleanup
}, []);

Optimize State Management: Use lightweight libraries like zustand or the Context API for simple use cases.

7. Use Native Modules Wisely

For heavy computations, offload tasks to native modules using react-native-bridge. This prevents the JavaScript thread from being blocked.

8. Minimize Third-Party Dependencies

Every dependency adds overhead. Use only essential libraries and periodically audit them for updates or removal.

Learning these techniques not only enhances your app’s performance but also boosts your chances of securing a job at leading companies.

Most Commonly Asked React-Native Interview question

Improving Application Performance in React Native