test.html

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<script type="text/javascript" src="https://www.gstatic.com/firebasejs/3.7.1/firebase.js"></script>

	<script>
	  var app = firebase.initializeApp({
	    apiKey: 'AIzaSyBvayAXTAGGkstA9aFudzcY6mUtErLPxa4',
	    authDomain: 'mobx-firebase.firebaseapp.com',
	    databaseURL: 'https://mobx-firebase.firebaseio.com',
	    storageBucket: '<your-storage-bucket>',
	    messagingSenderId: 'mobx-firebase.appspot.com'
	  });
	
	</script>

</head>
<body>
	
</body>
</html>