index.js:19 Uncaught TypeError: firebase.ref is not a function code example

Example 1: firebase.database is not a function

<script src="https://www.gstatic.com/firebasejs/7.24.0/firebase-auth.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.24.0/firebase-database.js"></script>
// don't forget to change the "7.24.0" part of the url with the current version

Example 2: firebase.database is not a function

<script src="https://www.gstatic.com/firebasejs/3.1.0/firebase-auth.js"></script>
<script src="https://www.gstatic.com/firebasejs/3.1.0/firebase-database.js"></script>