React Native is a popular framework for building cross-platform mobile applications. Upon deciding to use React Native, developers often face the challenge of choosing the right tool or library to enhance their workflow. One such library is Hermes.
What is Hermes?
Hermes is an open-source JavaScript engine optimized for React Native applications. It was developed by Facebook and released in 2019. Its primary focus is on improving the startup time, reducing memory usage and improving the overall performance of React Native apps.
How does Hermes work?
Hermes replaces the default JavaScript engine that comes with React Native. It uses a technique called ahead-of-time (AOT) compilation, which compiles JavaScript code into bytecode before runtime. This approach provides several benefits such as reduced parsing time, faster startup time, and decreased memory usage.
What are the advantages of using Hermes?
- Better performance: As mentioned earlier, Hermes has been optimized for React Native applications. It reduces the amount of time it takes for your app to start up and speeds up your app’s overall performance.
- Reduced memory usage: By using AOT compilation, Hermes can reduce your app’s memory footprint by up to 20% compared to other JavaScript engines like V8.
- Faster startup time: With its AOT compilation technique, Hermes can compile your app’s source code into bytecode before runtime; this results in faster app startup times.
Are there any disadvantages to using Hermes?
One disadvantage of using Hermes is that it’s only compatible with Android devices running version 5.0 (Lollipop) or later. If you’re developing an iOS application or need compatibility with older Android versions, you’ll have to look elsewhere.
How to enable Hermes in your React Native app
Enabling Hermes in your React Native app is relatively easy. First, make sure you have the latest version of the React Native CLI installed. Then, open your app’s android/app/build.gradle file and add the following lines of code:
“`
project.ext.react = [
entryFile: “index.js”,
enableHermes: true // <- Add this line
]
```
Save the file and rebuild your app.
Conclusion
Hermes is an excellent choice for developers who want to improve their React Native apps’ performance, reduce memory usage, and speed up startup times. It’s easy to enable and can provide significant benefits to your app’s performance. However, it’s important to note that Hermes is only compatible with Android devices running version 5.0 or later.