React Native covers most of the components and APIs that are available in iOS and Android. Points such as UI components, navigation, or networking can be fully set up within our JavaScript code using React Native components, but not all the platform's capabilities have been mapped from the native world to the JavaScript world. Nonetheless, React Native offers a way to write real native code and have access to the full power of the platform. If React Native doesn't support a native feature that you need, you should be able to build it yourself.
In this chapter, we are going to use React Native's ability to enable our JavaScript code to communicate with custom native code; specifically, we will write a native module to detect frequencies coming from the device's microphone. These capabilities shouldn't be part of the day-to-day tasks for a React...
