How to push notification in NuxtJS with Firebase Cloud Messaging

index.vue

<template></template>

<script>
import firebase from '../plugins/firebase';
export defautl {
  created() {
      const messaging = firebase.messaging();
      messaging
        .requestPermission()
        .then(() => {
          console.log('Notification permission granted.');
           return messaging.getToken();
        })
        .then((token) => {
          // You update this token for server by call api
          console.log('The token is: ', token);
        })
        .catch(function (err) {
           console.log('Unable to get permission to notify.', err);
        });
  }
}
</script>