Firebase data is "undefined" when it is not

Question

I am trying to retrieve some data from my firebase database, but the value I get is "undefined".

This is how I save the data to the database:

var database = firebase.database();

        database.ref().push({
        mainArray: mainArray,
        secondArray: secondArray,
        listname: listName,
        mainLanguage: mainLanguage,
        secondLanguage: secondLanguage,

  }, function(error) {
  if (error){

    stopLoader();

    showSnackbar("An error has occured! Please try again later.");
}

This is how I read the data, but the value of listname is "undefined":

 var database = firebase.database().ref().child('codes');
    var codeInput = document.getElementById('mainSearch');

    database.on('value', function(snapshot) {
            if (!snapshot.hasChild(codeInput.value)) {

                codeInput.value = "";
                showSnackbar("A list with this code does not exist!<br><br>Please try another one.")
            }
            else {

               var data = snapshot.val();
               var listname = data.listname;


               console.log(listname);



            }
        });

This is the value I get from the database:

This is how the data is structured in the database:

Solution

I changed my code to this and now it works perfectly. The problem was that i was trying to get the value from the wrong child. Thanks for your help and patience!

var database = firebase.database().ref().child('codes');
var codeInput = document.getElementById('mainSearch');


database.child(codeInput).on('value', function(snap) {

          var data = snap.val();

          var listName = data.listname;
          var mainLanguage = data.mainLanguage;
          var secondLanguage = data.secondLanguage;
          var mainArray = data.mainArray;
          var secondArray = data.secondArray;

        });