updated App.js

App.js

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 * @flow
 */

import React, { Component } from 'react';
import {
  Platform,
  StyleSheet,
  Text,
  View
} from 'react-native';
import firebase from 'react-native-firebase';
import { Notification } from 'react-native-firebase';

const instructions = Platform.select({
  ios: 'Press Cmd+R to reload,\n' +
    'Cmd+D or shake for dev menu',
  android: 'Double tap R on your keyboard to reload,\n' +
    'Shake or press menu button for dev menu',
});

export default class App extends Component {


  componentDidMount() {
    firebase.messaging().hasPermission()
      .then(enabled => {
        if (enabled) {
          firebase.messaging().getToken().then(token => {
            console.log("LOG: ", token);
          })
          // user has permissions
        } else {
          firebase.messaging().requestPermission()
            .then(() => {
              alert("User Now Has Permission")
            })
            .catch(error => {
              console.log(error)
              alert("Error", error)
              // User has rejected permissions  
            });
        }
      });


    this.notificationListener = firebase.notifications().onNotification((notification) => {

      // Process your notification as required
      const {
        body,
        data,
        notificationId,
        sound,
        subtitle,
        title
      } = notification;
      console.log("LOG: ", title, body, JSON.stringify(data))
    });
  }


  componentWillUnmount() {
    this.notificationListener();
  }


  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>
          Welcome to React Native!
        </Text>
        <Text style={styles.instructions}>
          To get started, edit App.js
        </Text>
        <Text style={styles.instructions}>
          {instructions}
        </Text>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});