Hermes: An open source JavaScript engine optimized for mobile apps, starting with React Native

What this post added

This post introduces Hermes, an open-source JavaScript engine specifically designed to improve the performance of mobile applications, particularly those built with React Native. Key technical contributions include bytecode precompilation for faster startup and smaller app size, the absence of a Just-In-Time (JIT) compiler to avoid impacting TTI and memory usage, and a specialized garbage collector strategy optimized for mobile device constraints. It also details developer experience improvements like lazy compilation for faster iteration during development and Chrome remote debugging support. The post also highlights the role of JSI in enabling further React Native infrastructure improvements like Fabric and TurboModules.