index.html

<!DOCTYPE html>
<html lang="en">

<head>

    <meta name="google-signin-client_id"
        content="224025770478-fgnvdgjp81e9rfs2nig83innciis9n4u.apps.googleusercontent.com">
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://apis.google.com/js/platform.js" async defer></script>
    <script type="text/javascript" src="memlist.json"></script>
    
    <script src="https://www.gstatic.com/firebasejs/8.6.8/firebase.js"></script>
    <!-- TODO: Add SDKs for Firebase products that you want to use
     https://firebase.google.com/docs/web/setup#available-libraries -->
    
</head>

<body>

    <div class="g-signin2" data-onsuccess="onSignIn"></div>
    <button>
        <a href="https://chat.whatsapp.com/KXOcJf5DIKkKvkkumDijVt">
            Test Link
        </a>
    </button>
    <script>

        var email;

        var firebaseConfig = {
            apiKey: "AIzaSyBpJ50cUazZkRyAquQ9hNyckJO6HchuRPg",
            authDomain: "telegramauth2.firebaseapp.com",
            databaseURL: "https://telegramauth2-default-rtdb.firebaseio.com",
            projectId: "telegramauth2",
            storageBucket: "telegramauth2.appspot.com",
            messagingSenderId: "762660936918",
            appId: "1:762660936918:web:6db63fb3c7265619babd77",
            measurementId: "G-KZFM2WBCLK"
        };
        // Initialize Firebase
        firebase.initializeApp(firebaseConfig);
        //firebase.analytics();
        var database = firebase.database();

        const dbRef = firebase.database().ref();

        function onSignIn(googleUser) {
            var profile = googleUser.getBasicProfile();
            email = profile.getEmail();
            console.log('ID: ' + profile.getId()); // Do not send to your backend! Use an ID token instead.
            console.log('Name: ' + profile.getName());
            console.log('Image URL: ' + profile.getImageUrl());
            console.log('Email: ' + profile.getEmail()); // This is null if the 'email' scope is not present.
            dbRef.child("0").child(email).get().then((snapshot) => {
                if (snapshot.exists()) {
                    console.log(snapshot.val());
                } else {
                    console.log("No data available");
                }
            }).catch((error) => {
                console.error(error);
            });
        }


        

        //var abcd = [{"name" : "sandeep"},{"name" :"Ramesh"}];
        //abcd = JSON.parse(abcd);
        //for (var index = 0; index < abcd.length; index++) {
        //    alert(abcd[i].name);
        //}

    </script>
</body>

</html>