Aman Kumar
  7 Nov 24

React Native is a powerful framework for building cross-platform mobile apps, but like any technology, performance can be a concern when dealing with complex apps. To ensure that your React Native app performs smoothly, it’s crucial to apply best practices in performance optimization. In this blog post, I’ll cover some essential tips to help boost the performance of your React Native app.

1. Use Memoization and Caching Techniques

Memoization helps avoid recalculating results when they are not needed. React’s memo, useMemo, and useCallback hooks can be used to optimize performance by caching function results and values.

import React, { useMemo, useCallback } from 'react';

const MyComponent = ({ data }) => {
  const memoizedValue = useMemo(() => expensiveComputation(data), [data]);

  const handleClick = useCallback(() => {
    console.log('Clicked');
  }, []);

  return (
    <div onClick={handleClick}>
      {memoizedValue}
    </div>
  );
};

2. Optimize Images and Assets

Large image files can slow down your app. By compressing images, using the correct file formats, and implementing lazy loading, you can enhance your app’s performance. You can use libraries like react-native-fast-image for better image loading performance.

To install npm install react-native–fast-image

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

<FastImage
  style={{ width: 200, height: 200 }}
  source={{
    uri: 'https://your-image-url.com/photo.jpg',
    priority: FastImage.priority.high,
  }}
  resizeMode={FastImage.resizeMode.contain}
/>

3. Avoid Unnecessary Re-renders

One common issue is excessive re-renders, which can significantly degrade performance. You can prevent unnecessary re-renders by using React.memo, shouldComponentUpdate lifecycle method, and pure components.

const MemoizedComponent = React.memo(({ data }) => {
  return <Text>{data}</Text>;
});

4. FlatList and SectionList Optimization

When rendering large lists in React Native, always prefer FlatList or SectionList over the basic ScrollView. Additionally, make sure to use keyExtractor and getItemLayout for efficient rendering.

<FlatList
  data={data}
  keyExtractor={(item) => item.id}
  getItemLayout={(data, index) => (
    { length: ITEM_HEIGHT, offset: ITEM_HEIGHT * index, index }
  )}
  initialNumToRender={10}
  renderItem={({ item }) => <ItemComponent item={item} />}
/>

5. Reduce JavaScript Overload

To install -  npm install react-native-reanimated


import Animated, { Easing } from 'react-native-reanimated';

const animation = new Animated.Value(0);

Animated.timing(animation, {
  toValue: 1,
  duration: 500,
  easing: Easing.linear,
}).start();

6. Enable Hermes Engine

Hermes is an open-source JavaScript engine that optimizes the execution of your React Native app, reducing startup time and improving performance.

To enable Hermes in your project:

1. Open android/app/build.gradle.
2. Add the following code:
   

   project.ext.react = [   enableHermes: true,  // enable Hermes for better performance