6 Tips to Optimize React Native App Performance

6 Tips to Optimize React Native App Performance

Using a mobile app should be an enjoyable experience, without any frustrating delays. As a React Native developer, it’s crucial that you optimize your apps, so they work well and are easy to use. Peak app performance requires you to write clean and efficient code using the right tools and libraries.

Take a look at these tips and techniques to optimize the performance of your React Native app.

1. Reduce Unnecessary Re-Renders With useMemo Hook

React Native renders components using a Virtual DOM (VDOM) technology. The VDOM keeps track of all changes to the app component and re-renders the entire view hierarchy when it deems necessary. This process is expensive, so you should avoid unnecessary updates to the component’s state and props.

The React library provides the useMemo and useCallback hooks to solve this problem in functional components. You can use the useMemo hook to memoize the resulting value of a JavaScript function that you don’t want to recompute on every render.

Here’s an example of how you can use the useMemo hook:

import { useMemo } from 'react';

function MyComponent({ data }) {
  // The computeExpensiveValue function is an expensive computation that
  // doesn't need to be re-computed on every render.
  const expensiveValue = useMemo(() => computeExpensiveValue(data), [data]);


  // The component can use the memoized value without re-computing
  // it on every render.
  return <div>{expensiveValue}</div>;
}

Wrapping the computeExpensiveValue function inside the useMemo hook memoizes the result of the function. The useMemo hook can accept a second argument as a dependency. This means the memoized function will only run gain when this dependency changes.

useCallback is similar to useMemo, but it memoizes a callback function instead of a value. This can be useful for preventing unnecessary re-renders of child components triggered by a callback function passed down as a prop.

2. Effective State Data Handling

Poor state management can lead to data inconsistencies, leading to unexpected behavior that can be difficult to track down and fix. Good state management involves avoiding storing unnecessary data in the state, which can slow down the app and make it harder to debug. It is important to ensure that all state you store is absolutely necessary for the component to render.

Another way to update state effectively is to use immutability techniques, like the spread operator or the Object.assign() method.

For example:

import React, { useState } from 'react';

function MyComponent() {
  const [state, setState] = useState({
    count: 0,
    text: 'Hello'
  });

  function handleClick() {
    setState(prevState => {
      return Object.assign({}, prevState, { count: prevState.count + 1 });
    });
  }

  return (
    <div>
      <button onClick={handleClick}>Increment Count</button>
    </div>
  );
}

In this example, the handleClick function uses the setState hook to update the state. Still, instead of directly modifying the state object, it uses the Object.assign() method to create a new object that copies the previous state with the count property modified. This approach allows React’s virtual DOM to re-render the component when it recognizes that you’ve updated the state.

You can also use a state management library like Redux and the built-in context API to implement this technique.

3. Implement a Performance Monitoring System

Mobile app performance monitoring systems (PMS) are tools that let you measure and analyze the performance of your mobile apps. They provide features such as real-time monitoring, crash reporting, network monitoring, performance metrics, and user session replay. Using a performance monitoring system with your React Native app will allow you to identify performance bottlenecks to fix and scale your app.

Here is a list of several PMC tools available.

  • React Native Debugger: A standalone app that lets you debug and inspect the state of your React Native app. It also includes a performance monitor to help you identify and fix performance issues.
  • React Native Profiler: This built-in performance monitoring tool allows you to watch your app’s performance by measuring the time it takes to render each component.
  • Flipper: A mobile app development platform with a performance monitor that can help you identify and fix performance issues.
  • Firebase Performance Monitoring: A performance monitoring tool provided by Firebase that allows you to track the performance of your app on different devices and platforms.

4. Remove Console.log Statements

When a console.log statement runs, it sends a message to the JavaScript engine to log the message to the console. The JS engine then takes time to process and display the message.

Too many console statements in your code will slow down its execution and cause performance delays. This can be especially problematic when your app runs on a device with limited resources, such as a low-end mobile device.

A react native metro terminal with several console logs and an error message

5. Build an Efficient Navigation System

A good navigation system will improve the overall structure of your React Native app, making it easier to maintain, update features, and pass state data around efficiently. Additionally, it makes switching between multiple displays in your application much easier, improving the user experience.

man drawing a navigation story board on paper with an iPhone on a table

You should consider factors like the right navigation pattern (tab-based, stack-based, drawer-based, etc.) to suit your app. Take into account the number of screens you expect in your app, and how you will pass state data between them.

Caching is a useful method for developing a reliable navigation system. Caching allows you to save the state of a screen or component when the user leaves it, then restore it when they return. This helps minimize the amount of data that you need to load and the number of times you need to re-render.

React Native has several libraries available for navigation, such as React Navigation and React Native Navigation. You can use them to implement some of these common navigation patterns in your app.

6. Reduce App Size With Code Splitting and Lazy Loading

App size is important for optimized performance because it can affect aspects of the user experience, like initial load time, memory usage, and storage space.

Code splitting and lazy loading are techniques that can reduce your React Native app’s size and improve performance.

Code splitting is the process of breaking down a large JavaScript code base into smaller, more manageable “bundles.”This can significantly reduce the initial load time of the app.

Lazy loading is a technique that allows you to load components as the user navigates to them rather than on startup. This can help reduce the amount of memory your app uses and improve overall performance.

Why Performance Optimization Is Important

Performance optimization is crucial for the success of any mobile app. A slow app can lead to poor user experience and ultimately result in low engagement and retention.

These tricks are only a few ways you can utilize to ensure an enjoyable experience for your app’s user base.

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