This repository shows the usage of custom C++ code to be used in a React Native project. The benefits are shared code between Android and iOS, as well as performance benefits for certain algorithms.
Have a look at react-native-cpp-code for the React Native module and C++ code.
Since this repository originated from the official React Native template, you can follow its instructions, using the React Native CLI:
yarn
react-native run-android
react-native run-ios