About this BookIn mobile development, there is a trade-off between portability code and fast execution. A new feature of React Native called JavaScript Native Interface (JSI) removes that trade-off by allowing developers to write portable code that executes as binary code on the native device.What You Will LearnThis book teaches you how to write JSI code so that you can have write-once, run-everywhere mobile apps that feel like they are written in native code.You will learn how to set up a JSI project on MacOS, Windows, and Linux. It will teach you how to register native functions, and how to accept any type of parameter and return any type of value. Importantly, this also includes working with objects, arrays, callback functions, and promises.Who This Book Is ForThis book is intended for programmers, engineers, and technology enthusiasts who want to learn about mobile development.