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6 Tips to Optimize React Native App Performance

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Shivam Mehta
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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

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