//Create Firebase-messaging-sw.js where you want
firebase.js
 
import { initializeApp } from "firebase/app";
import { getMessaging, getToken } from "firebase/messaging";

const firebaseConfig = {
    apiKey: "",
    authDomain: "",
    projectId: "",
    storageBucket: "",
    messagingSenderId: "",
    appId: ""
};

const firebaseApp = initializeApp(firebaseConfig);
const messaging = getMessaging(firebaseApp);

export const getToken1 = () => {

    console.log('Requesting permission...');
    if (navigator.serviceWorker) {
        navigator.serviceWorker
            .register(`fullpath-to-/firebase-messaging-sw.js`)
            .then((registration) => {
                Notification.requestPermission().then((permission) => {
                    if (permission === 'granted') {
                        return getToken(messaging, { vapidKey: "your vapid", serviceWorkerRegistration: registration }).then((currentToken) => {
                            if (currentToken) {
                                console.log('current token for client: ', currentToken);

                                // Track the token -> client mapping, by sending to backend server
                                // show on the UI that permission is secured
                            } else {
                                console.log('No registration token available. Request permission to generate one.');

                                // shows on the UI that permission is required 
                            }
                        }).catch((err) => {
                            console.log('An error occurred while retrieving token. ', err);
                            // catch error while creating client token
                        })
                    }
                })
            })
            .catch((error) => {
                console.error('Service Worker registration failed:', error);
            });

          }
       

    }