problem get token

[spikepower]

when I allow it to send notifications it tells me

Notification permission granted. (index):62 An error occurred while retrieving token. ReferenceError: $ is not defined at saveToken ((index):73) at (index):53

firebase.initializeApp(config); // Retrieve Firebase Messaging object. const messaging = firebase.messaging(); messaging.requestPermission() .then(function() { console.log('Notification permission granted.'); // TODO(developer): Retrieve an Instance ID token for use with FCM. if(isTokenSentToServer()) { console.log('Token already saved.'); } else { getRegToken(); } }) .catch(function(err) { console.log('Unable to get permission to notify.', err); }); function getRegToken(argument) { messaging.getToken() .then(function(currentToken) { if (currentToken) { saveToken(currentToken); console.log(currentToken); setTokenSentToServer(true); } else { console.log('No Instance ID token available. Request permission to generate one.'); setTokenSentToServer(false); } }) .catch(function(err) { console.log('An error occurred while retrieving token. ', err); setTokenSentToServer(false); }); } function setTokenSentToServer(sent) { window.localStorage.setItem('sentToServer', sent ? 1 : 0); } function isTokenSentToServer() { return window.localStorage.getItem('sentToServer') == 1; } function saveToken(currentToken) { $.ajax({ url: 'action.php', method: 'post', data: 'token=' + currentToken }).done(function(result){ console.log(result); }) } messaging.onMessage(function(payload) { console.log("Message received. ", payload); notificationTitle = payload.data.title; notificationOptions = { body: payload.data.body, icon: payload.data.icon, image: payload.data.image }; var notification = new Notification(notificationTitle,notificationOptions); });

how fix this problem?