<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Welcome to Firebase Hosting</title>

    <!-- update the version number as needed -->
    <script defer src="/__/firebase/7.19.0/firebase-app.js"></script>
    <!-- include only the Firebase features as you need -->
    <script defer src="/__/firebase/7.19.0/firebase-auth.js"></script>
	   <script defer src="/__/firebase/7.19.0/firebase-firestore.js"></script>
    <script defer src="/__/firebase/7.19.0/firebase-database.js"></script>
    <script defer src="/__/firebase/7.19.0/firebase-messaging.js"></script>
    <script defer src="/__/firebase/7.19.0/firebase-storage.js"></script>
    <!-- initialize the SDK after all desired features are loaded -->
    <script defer src="/__/firebase/init.js"></script>

   <script>
   
   db.collection("test").doc("userid")
    .onSnapshot(function(snapshot) {
        snapshot.docChanges().forEach(function(change) {
            if (change.type === "added") {
                console.log("New city: ", change.doc.data());
            }
            if (change.type === "modified") {
                console.log("Modified city: ", change.doc.data());
            }
            if (change.type === "removed") {
                console.log("Removed city: ", change.doc.data());
            }
        });
    });
   
   </script>
  </head>
  <body>
   
   
   
   
   
   
   
   
   
   
  
  </body>
</html>
