React Native is a popular framework for developing cross-platform mobile applications. It allows developers to build native mobile apps using JavaScript and React, which can then be deployed on both iOS and Android platforms.
One of the challenges while building an app in React Native is to handle network requests and manage data flow. This is where Hermes for React Native comes into play.
What is Hermes for React Native?
Hermes is an open-source JavaScript engine that was developed by Facebook to improve the performance of React Native apps. It is designed specifically for mobile devices and is optimized for low memory usage, fast startup time, and small binary size.
Hermes provides a more efficient runtime environment for JavaScript code than the default engine used by React Native, which is based on JavaScriptCore. It achieves this by using ahead-of-time (AOT) compilation instead of just-in-time (JIT) compilation. This means that Hermes compiles your JavaScript code into machine code before it’s executed, which results in faster performance and lower memory usage.
Why Use Hermes for React Native?
There are several benefits to using Hermes in your React Native projects:
- Better Performance: As mentioned earlier, Hermes offers better performance than the default JavaScript engine used by React Native. This means that your app will run faster and smoother, even on older or lower-end devices.
- Lower Memory Usage: Since Hermes uses AOT compilation instead of JIT compilation, it’s able to reduce the amount of memory that’s required to run your app.
- Faster Startup Time: Because Hermes compiles your code ahead of time, your app will start up faster than if it were using the default engine.
- Smaller Binary Size: By optimizing the way that JavaScript code is compiled and executed, Hermes is able to produce smaller binary files for your app. This can be especially important if you’re Targeting devices with limited storage capacity.
How to Use Hermes for React Native
To use Hermes in your React Native project, you’ll need to make a few changes to your project configuration. Here’s how:
Step 1: Update Your Android Build Configuration
If you’re building your app for Android, you’ll need to update your build.gradle file to include the Hermes engine. To do this, add the following lines to the android section of your file:
project.ext.react = [
enableHermes: true
]
This will enable Hermes as the JavaScript engine for your app on Android.
Step 2: Update Your iOS Build Configuration
If you’re building your app for iOS, you’ll need to update your Xcode project settings. Specifically, you’ll need to set the JavaScriptEngine property of your AppDelegate.m file to use the Hermes engine. Here’s how:
#import#import #import @implementation AppDelegate - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { RCTBridge *bridge = [[RCTBridge alloc] initWithDelegate:self launchOptions:launchOptions]; RCTRootView *rootView = [[RCTRootView alloc] initWithBridge:bridge moduleName:@"YourApp" initialProperties:nil]; // Set the JavaScript engine to use Hermes rootView.appProperties = @{@"JavaScriptEngine": @"hermes"}; rootView.backgroundColor = [[UIColor alloc] initWithRed:1.0f green:1.0f blue:1.0f alpha:1]; self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds]; UIViewController *rootViewController = [UIViewController new]; rootViewController.view = rootView; self.window.rootViewController = rootViewController; [self.window makeKeyAndVisible]; return YES; } @end
Conclusion
Hermes is a powerful tool for improving the performance and memory usage of your React Native apps. By optimizing the way that JavaScript code is compiled and executed, it’s able to provide faster startup times, smaller binary sizes, and smoother overall performance. If you’re building a mobile app with React Native, it’s definitely worth considering Hermes as your JavaScript engine of choice.