How to retireve data from firebase in web with js

I have buttons similar to the one here A3. I want to check the availability of the seat from my database and do accordingly in the if loop.. but none of my functions below the firebase reference is working

My database is

My web (app) | Seats(node) | Status (node) | A1 - available (value) A2 - available (value) A3 - available (value) A4 - available (value)

And my js script is

function A3(){
  var newseat = document.getElementById("A3");
  var firebaseStatusRef = firebase.database().ref().child("Status"); 
  var firebaseSeatStatusRef = firebaseStatusRef.child("A3");

  firebaseSeatStatusRef.on('child_added', snap => {
    var seatStatus = snap.val();
  });

if (firebaseSeatStatusRef=="available") {
  newseat.className="booked-seat";
  newseat.setAttribute("class" , "booked-seat");
  firebaseStatusRef.child("A3").set("booked");
  var fill = newseat.value;
document.getElementById("fill").value += fill + " ";
Seat();

} else  {

  newseat.style.backgroundColor = 'seat';
  newseat.setAttribute("class" , "seat");
  var fill = newseat.value;
document.getElementById("fill").value -=  fill + " ";
BookedSeat();

}

}