That's not entirely true. React Native does indeed run on the native device, not in a JS "container". The JS part is a bit of glue code. In the case of iOS for

That's not entirely true. React Native does indeed run on the native device, not in a JS "container". The JS part is a bit of glue code. In the case of iOS for example, React Native uses the same exact UI toolkit that runs natively on the iPhone as if you have written it in Swift or Objective-C. Apple's JavaScriptCore exposes the native elements with a JS api, but they are not running inside JS. Only a minor part of the glue is interpreted as JS, and it's not usually the CPU-intensive stuff.