React Native is an open-source framework for building mobile applications using JavaScript and React. It allows developers to create high-quality, native mobile apps for both iOS and Android platforms.
Within React Native, there is a popular library called Hermes that is used to improve the performance of JavaScript code. In this article, we will explore how Hermes works in React Native.
What is Hermes?
Hermes is an open-source JavaScript engine that was created by Facebook. It is designed to optimize the performance of JavaScript code on mobile devices. By using Hermes, developers can achieve faster startup times, lower memory usage, and smoother animations in their React Native apps.
How does Hermes work?
Hermes works by converting JavaScript code into bytecode that can be executed by the device’s CPU. This bytecode is then optimized and stored in memory for faster access. The use of bytecode allows Hermes to reduce the amount of time it takes to parse and execute JavaScript code compared to other engines.
Another way that Hermes improves performance is through its garbage collection system. Garbage collection refers to the process of freeing up memory that is no longer being used by an application.
In traditional JavaScript engines, garbage collection can cause pauses in the application’s execution, which can lead to stuttering animations and slower performance. However, Hermes uses a more efficient garbage collection system that minimizes these pauses.
How to enable Hermes in a React Native app?
Enabling Hermes in a React Native app is a straightforward process. First, make sure you have the latest version of React Native installed on your machine. Then, open your project’s metro.config.js file and add the following code:
“`
module.exports = {
resolver: {
sourceExts: [‘jsx’, ‘js’, ‘ts’, ‘tsx’], //add all needed extensions
},
transformer: {
assetPlugins: [‘expo-asset/tools/hashAssetFiles’],
babelTransformerPath: require.resolve(‘react-native-svg-transformer’),
getTransformOptions: async () => ({
transform: {
experimentalImportSupport: false,
inlineRequires: false,
},
}),
},
server: {
useGlobalHotkey: true,
port: 8081,
},
serializer: {
getModulesRunBeforeMainModule() {
return [
require.resolve(
‘/node_modules/react-native/Libraries/Core/InitializeCore.js’
),
];
},
getPolyfills: () => require(‘/path/to/polyfills.js’),
},
};
“`
Once you have added this code, rebuild your app by running the following command:
“`
react-native run-android
“`
or
“`
react-native run-ios
“`
After the rebuild is complete, you should see improved performance in your application.
Conclusion
Hermes is a powerful tool that can greatly improve the performance of React Native applications. It works by optimizing JavaScript code and using an efficient garbage collection system.
Enabling Hermes in a React Native app is a simple process that can be done by adding a few lines of code to your metro.js file. By leveraging the power of Hermes, developers can create high-quality mobile apps that provide a seamless user experience.