There are several ways to write cross-platform apps. Cordova (PhoneGap) and Xamarin are two solutions which are widely being used by many developers. When Skype team decided to choose a cross-platform framework to write their client, neither Cordova nor Xamarin suited their needs. Web wrappers like Cordova (PhoneGap) didn’t provide the performance or “native feel” they were looking for. Even though Xamarin is a great solution for cross-platform mobile development, it didn’t help them on the web. In order to maximize their engineering efficiency and agility, Skype team decided to build their new client on top of React JS and React Native. ReactXP unifies the behaviors and interfaces across React JS and the various React Native implementations.
ReactXP is a thin, lightweight cross-platform abstraction layer on top of React and React Native. It implements the foundational components that can be used to build more complex components. It also implements a collection of API namespaces that are required by most applications. It supports the following platforms: web (React JS), iOS (React Native), Android (React Native) and Windows UWP (React Native). Microsoft recently announced that they are open-sourcing ReactXP framework. They are planning to release a new version of ReactXP approximately monthly, roughly aligned to React Native releases.
You can learn more about ReactXP framework here.