Here's one Module from Kim Døfler that we really like. It will let you use the iOS native Twitter and Facebook share popup in React Native.

react-native-social-share

Use the build in share view from iOS to let the user share on Facebook and Twitter. It will use the users existing account without having to get new authorizations. You can even preset text, image and link for the share view.

In other words a React Native wrapper for the SLComposeViewController