getting started React Native

gettingstarted.js

import React, { useState } from 'react';
import { StyleSheet, Text, View, TextInput, Button, Alert } from 'react-native';

export default function App() {
  const [ text, setText ] = useState("This is our message on Screen"); 
  const [ todo, setTodo ] = useState("");
  addTodo = () => {
    setTodo(text);
    Alert.alert('Alert Box', "Oops you Touch Me!");
  }
  return (
    <View style={styles.container}>
      <Text>Open up App.js to start working on your !</Text>
      <TextInput 
        style={styles.inputStyle}
        onChangeText={(text) => setText(text)}
      />
      <Button 
        title="Add Todo"
        onPress={this.addTodo}
      />
      <Text>{todo}</Text>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#ffffff',
    alignItems: 'center',
    justifyContent: 'center',
  },
  inputStyle: {
    height: 40,
    borderColor: "green",
    borderWidth: 1,
  }
});