signedin.html

<!DOCTYPE html>
<html lang="en">

<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Firebase ID Token Generator</title>

	<style>
		* {
			box-sizing: border-box;
		}
		#idToken {
			width: 100%;
		}
	</style>
</head>

<body>

	<button onclick="getIdToken()">GET</button>
	<button onclick="getIdToken(true)">GET (force new)</button>
	<button onclick="copy()">Copy</button>
	<button onclick="firebase.auth().signOut()">Sign Out</button>
	<textarea id="idToken" rows="10" readonly onclick="this.select()">please wait...</textarea>

	<script src="https://www.gstatic.com/firebasejs/7.11.0/firebase-app.js"></script>
	<script src="https://www.gstatic.com/firebasejs/7.11.0/firebase-auth.js"></script>
	<script src="firebaseConfig.js"></script>

	<script>
		firebase.initializeApp(firebaseConfig);

		firebase.auth().onAuthStateChanged(async user => {
			if (user) getIdToken();
			else window.location = 'index.html';
		});

		async function getIdToken(forceNew) {
			document.getElementById('idToken').textContent = 'please wait...';
			var idToken = await firebase.auth().currentUser.getIdToken(forceNew);
			document.getElementById('idToken').textContent = idToken;
		}

		function copy() {
			document.getElementById('idToken').select();
			document.execCommand("copy");
			alert('copied to clipboard');
		}

	</script>

</body>

</html>