Firebase获取子列表的子列表

{
  "parentList": {
    "childList1": {
      "grandchildList1": {
        "item1": "value1",
        "item2": "value2"
      },
      "grandchildList2": {
        "item3": "value3",
        "item4": "value4"
      }
    },
    "childList2": {
      "grandchildList3": {
        "item5": "value5",
        "item6": "value6"
      },
      "grandchildList4": {
        "item7": "value7",
        "item8": "value8"
      }
    }
  }
}

var parentListRef = firebase.database().ref('parentList');

var childList1Ref = parentListRef.child('childList1');
childList1Ref.on('value', function(snapshot) {
  snapshot.forEach(function(childSnapshot) {
    var grandchildListRef = childList1Ref.child(childSnapshot.key);
    grandchildListRef.on('value', function(grandchildSnapshot) {
      grandchildSnapshot.forEach(function(grandchildChildSnapshot) {
        console.log(grandchildChildSnapshot.key, grandchildChildSnapshot.val());
      });
    });
  });
});