Is Hermes Faster React Native?

React Native is a popular framework for building mobile applications that has gained a lot of attention over the past few years. It allows developers to write code once and deploy it on both iOS and Android platforms, saving them time and effort. However, one common question that arises is whether Hermes is faster than React Native.

What is Hermes?
Hermes is an open-source JavaScript engine optimized for React Native. It was developed by Facebook in 2019 with the aim of improving the performance of React Native applications.

Unlike other JavaScript engines, Hermes uses ahead-of-time (AOT) compilation instead of just-in-time (JIT) compilation. This means that it compiles your JavaScript code into bytecode before runtime, resulting in faster startup times and lower memory usage.

Is Hermes faster than React Native?
Yes, Hermes is faster than React Native in terms of startup time and memory usage. According to Facebook’s benchmarks, apps using Hermes have 20-30% faster startup times compared to those using the default JavaScript engine in React Native. Additionally, they saw a 2-3x reduction in memory usage when using Hermes.

• Startup time: The startup time of an application refers to the time taken by the app to launch from a cold start i.e., when you first open it after closing it completely. Using Hermes significantly reduces this time.
• Memory usage: Memory usage refers to the amount of RAM used by an application while running. Using Hermes optimizes this as well.

How to use Hermes in your React Native app?

Using Hermes in your React Native app is straightforward:

1. Add “hermes-engine” as a dev dependency:

“`
yarn add hermes-engine –dev
“`

2. Add “hermesEngine” to your “react-native.config.js” file:

“`
module.exports = {
project: {
ios: {},
android: {},
},
hermes: {
commandPath: “./node_modules/hermes-engine/windows-bin/hermes”,
// Flags to pass to Hermes compiler.
// Make sure these are in the right order.
// See https://hermesengine.dev/docs/building-from-source/#advanced-usage
compilerFlags: [“-O”, “-output-source-map”],
},
};
“`

3. Run the following command to build and run your app using Hermes:

“`
npx react-native run-android –variant=hermesDebug
“`

Conclusion

In conclusion, Hermes is faster than the default JavaScript engine in React Native. It offers faster startup times and lower memory usage, making it a great option for developers looking to optimize their mobile applications. Using Hermes in your React Native app is simple and can be done by following a few steps.