React Native allows building a native Android or iOS app using Javascript.
Reference:
Facebook React Native
Facebook React
Articles:
Why You Should Consider React Native For Your Mobile App
React Native vs Native iOS/Android
React Native: Is it the end of native development?
Why I’m not a React Native Developer
Tutorials:
Facebook
Toptal
AppCoda
Kyle Banks
Smashing
Medium
Tutorials Point
Ray Wenderlich