react-native-halloween-setup2.js

class StartPage extends Component {
  render() {
    return (
          <TouchableHighlight onPress={() => this.props.handlePage("main")}>
            <Text style={styles.text}>Go to the MainPage</Text>
          </TouchableHighlight>
    );
  }
}

class MainPage extends Component {
  render() {
    return (
        <TouchableHighlight onPress={() => this.props.handlePage("start")}>
         <Text style={styles.text}>Go to the StartPage</Text>
       </TouchableHighlight>
    );
  }
}