Firebase Realtime database (JavaScript)

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     var firebaseConfig = {
        apiKey: "AIzaSyBHMiAD60UYu1V-R-5SxoKViiZVTMVk7wc",
        authDomain: "students-6cafd.firebaseapp.com",
        databaseURL: "https://students-6cafd.firebaseio.com",
        projectId: "students-6cafd",
        storageBucket: "students-6cafd.appspot.com",
        messagingSenderId: "988005708211",
        appId: "1:988005708211:web:17b9d1b1d7198821"
      };
      // Initialize Firebase
      firebase.initializeApp(firebaseConfig);
      
      let database = firebase.database()
      
     var firebaseConfig = {
        apiKey: "AIzaSyBHMiAD60UYu1V-R-5SxoKViiZVTMVk7wc",
        authDomain: "students-6cafd.firebaseapp.com",
        databaseURL: "https://students-6cafd.firebaseio.com",
        projectId: "students-6cafd",
        storageBucket: "students-6cafd.appspot.com",
        messagingSenderId: "988005708211",
        appId: "1:988005708211:web:17b9d1b1d7198821"
      };
      // Initialize Firebase
      firebase.initializeApp(firebaseConfig);
      
      var database = firebase.database()
      
     var firebaseConfig = {
        apiKey: "AIzaSyBHMiAD60UYu1V-R-5SxoKViiZVTMVk7wc",
        authDomain: "students-6cafd.firebaseapp.com",
        databaseURL: "https://students-6cafd.firebaseio.com",
        projectId: "students-6cafd",
        storageBucket: "students-6cafd.appspot.com",
        messagingSenderId: "988005708211",
        appId: "1:988005708211:web:17b9d1b1d7198821"
      };
      // Initialize Firebase
      firebase.initializeApp(firebaseConfig);
      
      var database = firebase.database()
      
     var firebaseConfig = {
        apiKey: "AIzaSyBHMiAD60UYu1V-R-5SxoKViiZVTMVk7wc",
        authDomain: "students-6cafd.firebaseapp.com",
        databaseURL: "https://students-6cafd.firebaseio.com",
        projectId: "students-6cafd",
        storageBucket: "students-6cafd.appspot.com",
        messagingSenderId: "988005708211",
        appId: "1:988005708211:web:17b9d1b1d7198821"
      };
      // Initialize Firebase
      firebase.initializeApp(firebaseConfig);
      
      var database = firebase.database()
      
     var firebaseConfig = {
        apiKey: "AIzaSyBHMiAD60UYu1V-R-5SxoKViiZVTMVk7wc",
        authDomain: "students-6cafd.firebaseapp.com",
        databaseURL: "https://students-6cafd.firebaseio.com",
        projectId: "students-6cafd",
        storageBucket: "students-6cafd.appspot.com",
        messagingSenderId: "988005708211",
        appId: "1:988005708211:web:17b9d1b1d7198821"
      };
      // Initialize Firebase
      firebase.initializeApp(firebaseConfig);
      
      var database = firebase.database()
      
     var firebaseConfig = {
        apiKey: "AIzaSyBHMiAD60UYu1V-R-5SxoKViiZVTMVk7wc",
        authDomain: "students-6cafd.firebaseapp.com",
        databaseURL: "https://students-6cafd.firebaseio.com",
        projectId: "students-6cafd",
        storageBucket: "students-6cafd.appspot.com",
        messagingSenderId: "988005708211",
        appId: "1:988005708211:web:17b9d1b1d7198821"
      };
      // Initialize Firebase
      firebase.initializeApp(firebaseConfig);
      
      var database = firebase.database()
      
     var firebaseConfig = {
        apiKey: "AIzaSyBHMiAD60UYu1V-R-5SxoKViiZVTMVk7wc",
        authDomain: "students-6cafd.firebaseapp.com",
        databaseURL: "https://students-6cafd.firebaseio.com",
        projectId: "students-6cafd",
        storageBucket: "students-6cafd.appspot.com",
        messagingSenderId: "988005708211",
        appId: "1:988005708211:web:17b9d1b1d7198821"
      };
      // Initialize Firebase
      firebase.initializeApp(firebaseConfig);
      
      var database = firebase.database()
    

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