How to add show more functionality in this?

Show more.. ;

  // This is my firebase Database. I want to fetch more data when user clicks on 
  show more button:

  const databaseRef = ref(database, "Location1");
  let tableData = document.querySelectorAll(".tableData")[0];
  onValue(databaseRef, (snapshot) => {
    tableData.innerHTML = "";
    snapshot.forEach(function (childSnapshot) {});
  });