Hermes JavaScript Engine Performance on iOS
Article Summary
Callstack brings Hermes to iOS with React Native 0.64, ending Android's monopoly on this performance-focused JavaScript engine. The results challenge assumptions about cross-platform optimization.
Hermes, Facebook's lightweight JavaScript engine originally built for Android, is now available on iOS as of React Native 0.64. Callstack published this technical breakdown in April 2021, examining real-world performance impacts when Hermes runs on Apple platforms.
Key Takeaways
- Hermes uses ahead-of-time compilation and bytecode precompilation for faster startup
- iOS support required custom compilation work for Apple's platform constraints
- Engine reduces memory footprint compared to JavaScriptCore on iOS
Critical Insight
Hermes on iOS delivers measurable performance gains through AOT compilation and reduced memory usage, making it a viable alternative to JavaScriptCore for React Native apps.
