how to use firebase in javascript code example

Example: firebase javascript

// Create Firebase project

// Create Web app in Firebase console

// Link project

var firebaseConfig = {
  apiKey: // apiKey,
  authDomain: // authDomain,
  databaseURL: // databaseURL,
  projectId: // projectId,
  storageBucket: // storageBucket,
  messagingSenderId: // messagingSenderId,
  appId: // appId,
  measurementId: // measurementId
};
firebase.initializeApp(firebaseConfig);

// Add your dependencies

//E.G.

<script src="https://www.gstatic.com/firebasejs/7.21.1/firebase-app.js"></script>