React Native is a pretty slick framework. Unlike Ionic and other hybrid mobile frameworks, it allows you to use web technologies (React and JavaScript) to build native mobile apps. There is no browser or WebView involved, so developing a mobile app with React Native is similar to using the native SDK, in that you’ll do all your testing on an emulator or device. There is no way to test it in your browser like there is with Ionic.

https://scotch.io/tutorials/build-a-react-native-app-and-authenticate-with-oauth-20