Bring Your Favorite Language to React Native

Pasiński describes how JavaScript connects to native platform code. The older JavaScript bridge serialized messages and communicated asynchronously; the New Architecture uses JSI for direct access to JavaScript engines and native data. TurboModules still rely on C or C++ to connect to platform languages such as Java, Kotlin, Swift, and Objective-C.

Building native code means handling separate targets, toolchains, and language boundaries for platforms such as iPhone, Android, and Windows. Pasiński presents WebAssembly as a shared, platform-agnostic target with explicit imports and exports. A module can only access capabilities supplied to it, such as a network function.

Polyen is a toolkit in active development that aims to provide Web API compatibility and near-native performance. It compiles WebAssembly modules back to C so they become part of the app and can connect to React Native through JSI. A bundler integration can let developers import a module reference and create an instance.

Because modules are compiled into the app, Polyen cannot dynamically load arbitrary code; Pasiński describes that as a security benefit. The project also lacks threading support in React Native and does not yet support every WebAssembly feature. He demonstrates a Rust crypto library computing a digest in an example app.