React Native is an open-source mobile application framework that allows developers to build high-quality mobile applications for both iOS and Android platforms using JavaScript and React. It is widely used by developers across the globe for its ease of use, flexibility, and quick development capabilities. One of the most popular frameworks built on top of React Native is Hermes.
What is Hermes?
Hermes is an open-source JavaScript engine optimized for React Native. It is designed to improve the startup time, reduce memory usage, and accelerate the overall performance of React Native applications. Hermes was developed by Facebook and released in 2019.
How does Hermes work with React Native?
When you build a React Native application using Hermes, it replaces the default JavaScript engine with a new one that is optimized for mobile devices. The new engine compiles your JavaScript code into bytecode during the build process. This bytecode can then be executed directly by the device’s operating system without going through an interpreter.
Benefits of using Hermes in React Native
- Better Performance: By replacing the default JavaScript engine with Hermes, your application can experience faster startup times and reduced memory usage. This can lead to a better user experience overall.
- Improved Reliability: Since Hermes compiles your code into bytecode during the build process, it can catch potential runtime errors before your application goes live.
- Easier Debugging: When you use Hermes in conjunction with debugging tools like Flipper, you can easily debug your application’s JavaScript code right from your desktop.
How to enable Hermes in a React Native project
Enabling Hermes in a React Native project is a straightforward process that involves making changes to your project’s configuration files. Here are the steps:
iOS
To enable Hermes in your iOS project, open the `ios/Podfile` file and add the following line:
“`pod ‘ReactCommon/hermes’“`
Then, run the following command:
“`cd ios && pod install“`
Finally, open your Xcode project and update the `AppDelegate.m` file with the following code:
“`js
#import
// ..
– (instancetype)init
{
if (self = [super init]) {
[self initializeFlipper];
[self initializeHermes];
}
return self;
}
– (void)initializeHermes
{
NSString *rootDir = [[[NSBundle mainBundle] bundlePath] stringByAppendingString:@”/assets”];
NSString *mainJsBundlePath = [NSString stringWithFormat:@”%@/%@”, rootDir, @”index.bundle”];
NSArray
_bridge = [[RCTBridge alloc] initWithBundleURL:[NSURL fileURLWithPath:mainJsBundlePath isDirectory:NO]
moduleProvider:nil
launchOptions:nil];
}
// .
“`
Android
To enable Hermes in your Android project, open the `android/app/build.gradle` file and add the following lines:
“`js
project.ext.react = [
enableHermes: true // add this line
]
“`
Then, rebuild your project using the following command:
“`npx react-native run-android –variant=release“`
Conclusion
Hermes is a powerful JavaScript engine that can significantly improve the performance and reliability of React Native applications. By enabling Hermes in your React Native projects, you can enhance your application’s user experience while reducing memory usage. If you haven’t already tried it out, give it a shot today!