React Native is a popular framework that allows developers to build mobile applications using JavaScript. One of the features that make React Native stand out is its ability to optimize app performance through the use of Hermes, a lightweight JavaScript engine.
In this tutorial, we’ll take a look at how you can enable Hermes in your React Native project and improve the performance of your app.
What is Hermes?
Hermes is an open-source JavaScript engine that was developed by Facebook specifically for use with React Native. It’s designed to improve the startup time and reduce memory usage of mobile apps built with React Native. Hermes is particularly useful for apps that need to handle large amounts of data and complex user interfaces.
How to enable Hermes in your React Native project
Enabling Hermes in your React Native project is a straightforward process. Here are the steps:
Step 1: First, make sure you have the latest version of React Native installed on your computer. You can do this by running the command:
“`
npm install -g react-native-cli
“`
Step 2: Create a new React Native project using the following command:
“`
npx react-native init myproject
“`
Step 3: Navigate into your project directory and install Hermes using the following command:
“`
npm install –save hermes-engine
“`
Step 4: Open up your `android/app/build.gradle` file and add the following lines at the bottom:
“`
project.ext.react = [
enableHermes: true, // clean and rebuild if changing
]
“`
This tells your app to use Hermes instead of the default JavaScript engine.
Note: If you’re using an older version of React Native (0.60 or below), you may need to update your `android/build.gradle` file as well. Add the following lines to the `dependencies` block:
“`
classpath(“com.android.tools.build:gradle:3.4.2”)
“`
Testing Hermes in your React Native app
Now that you’ve enabled Hermes in your React Native project, it’s time to test it out.
Step 1: Start your app by running the command:
“`
npx react-native run-android
“`
This will start your app on an Android emulator or a connected device.
Step 2: Open up your developer menu by pressing `Ctrl + M` (on Windows) or `Cmd + M` (on macOS). Select “Dev settings” from the menu.
Step 3: In the Dev settings menu, select “Debug server host & port for device”. Enter the IP address of your computer and the port number (default is 8081).
Step 4: Go back to the main Dev settings menu and select “Reload JS”.
If everything is set up correctly, you should see a message in your console that says “Hermes engine is running” when you reload your app.
Conclusion
Enabling Hermes in your React Native project can significantly improve the performance of your app. It’s a simple process that can be done by following a few steps. Remember to test Hermes in your app to ensure that everything is working correctly.
Now that you know how to enable Hermes in React Native, you can take advantage of its benefits and build faster, more efficient mobile apps.