Firebase Javascript：获取第一个孩子的ID

Question

我试图获取数据库中第一个孩子的ID，但它返回“undefined”。下面是我的代码，我的数据是如何构成的：

var database = firebase.database().ref(); 
var postsRef = database.child("posts"); 
postsRef.orderByChild("date").limitToFirst(1).once("value", function(snapshot) { 
    console.log(snapshot.ref.parent); 
}); 

这是我的数据是如何构成的：

posts 
    1 
     date 
     title 
     alias 
     timestamp 
    2 
     date 
     title 
     alias 
     timestamp 
    3 
     date 
     title 
     alias 
     timestamp 

Answer 1

var postsRef = database.child("posts"); 
postsRef.orderByChild("date").limitToFirst(1).once("value", function(snapshot) { 
    console.log(snapshot.key); 
}); 

https://firebase.google.com/docs/reference/js/firebase.database.Reference#limitToFirst https://firebase.google.com/docs/reference/js/firebase.database.Reference#key

Answer 2

var snapshotKey = snapshot.key; 
var snapshotData = snapshot.val();