Where does the business logic go in a React-native app?

Inside the React-Native documentation, I only see examples using props, states, styles, and rendering. Everything in App.js

Where is business logic supposed to go?

In particular, I would like to fetch URLs with GET/POST, and manipulate the data, before going in

render() {return (<View style={{ flexGrow: 1, alignItems: 'center', justifyContent: 'center'}}>    ...</View>);}

to render something on the screen.