used to retrieve dat from firebase realtime datastore
var playersRef = firebase.database().ref("players/");
playersRef.on("child_added", function(data, prevChildKey) {
var newPlayer = data.val();
console.log("name: " + newPlayer.name);
console.log("age: " + newPlayer.age);
console.log("number: " + newPlayer.number);
console.log("Previous Player: " + prevChildKey);
});