Hello I'm working on some firebase project and i can save my datas via javascript into firebase database. But i couldn't figure it out to auto increment child value (my child value is duyuru, you can see the details in the below) of my database. I'm sharing my code in below can you give me hints to solve this issue.

  <script>



      // Initialize Firebase

      var config = {

        apiKey: sample1,

        authDomain: sample2,

        databaseURL: sample3,

        storageBucket: sample4,

      };





      firebase.initializeApp(config);

      var database = firebase.database();



     firebase.initializeApp(config);

  var database = firebase.database();



  function writeUserData(userId, name, email, imageUrl) {

  var kategori1 =  document.getElementById(kategori).value;

  var duyuru1 = document.getElementById(duyuru).value;

  var name1 = document.getElementById(name).value;

  var email1 = document.getElementById(email).value;

  var imageUrl1 = document.getElementById(imageUrl).value;











  firebase.database().ref(kategori1 +/ + duyuru1).set({

    username: name1,

    email: email1,

    profile_picture : imageUrl1

  });

}



    </script>

and the out is like this

{

    duyuru1: {

        email: kjfdlkl,

        profile_picture: dsfsd,

        username: meraha

    }

}

I want to output data like;

{

    duyuru1: {

        email: kjfdlkl,

        profile_picture: dsfsd,

        username: meraha

    },



    duyuru2: {

        email: kjfdlkl,

        profile_picture: dsfsd,

        username: meraha

    }

}

duyuru (child value) section should be auto increment, That's what i wanted for. Thank you for your answers