Question

有没有办法让我检索值的名称？例如： data image

我想用黄色突出显示值名称。

但是，现在我只能得到： web page image

据我了解，以下代码仅返回玩家得分的值。

var childData = childSnapshot.val();

我可以做这样的事情来获取值名称吗？

var childValueName = childSnapshot.val().name;

这是我的Java代码：

  function PrintData()
  {
    var ref = firebase.database().ref('Score');
    var PrintData = document.getElementById('PrintOutData');

   ref.on("value", function(snapshot)
   {
     PrintData.innerText = "";
     snapshot.forEach(function(childSnapshot)
     {
       console.log("childSnapshot.key: " + childSnapshot.key);
       var childData = childSnapshot.val();
       let keys = Object.keys(childData)
        keys.forEach(key => {
            let value = childData[key.toString()];
            console.log("value: " + value);
            PrintData.innerText += childSnapshot.key + ": " + value +"\r";
        })
     });
   });
  }

我的html代码：

<button type="button" onclick="PrintData()">Print!</button>

如果我错了，请纠正我！谢谢。

Answer 1

Firebase有一个精通而精美的文档。根据{{3}}，当您将相对路径传递给child（）方法时，将返回datasnapshot

// Assume we have the following data in the Database:
{
 "name": {
 "first": "Ada",
 "last": "Lovelace"
 }
}

// Test for the existence of certain keys within a DataSnapshot
var ref = firebase.database().ref("users/ada");
 ref.once("value")
.then(function(snapshot) {
  var name = snapshot.child("name").val(); // {first:"Ada",last:"Lovelace"}
  var firstName = snapshot.child("name/first").val(); // "Ada"
  var lastName = snapshot.child("name").child("last").val(); // "Lovelace"
  var age = snapshot.child("age").val(); // null
});

Answer 2

以下内容可能对您有用：

firebase.database().ref('score').once('value', snap => {
  var data = snap.val() // should return => {User1: {GamePlay00: 3}, User2:
  {GamePlay00: 1}, ...}

  var users = Object.keys('data') should return // => [User1, User2, ...]

  var usersDatas = users.map(user_id => data[user_id]) // should return something like => [{gamePlay00: 3}, {gamePlay00:1}, ...]

  var value = usersDatas.map(game_play_id => game_play_id) // should return => [gamePlay00, gamePlay00...]
})

请参阅以下链接以获取更多文档：Object.keys Firebase Docs

Answer 3

我也坚持将Snapshot.forEach()用于较低级别：

var ref = firebase.database().ref('Score');
var PrintData = document.getElementById('PrintOutData');

ref.on("value", function(snapshot) {
  PrintData.innerText = "";
  snapshot.forEach(function(userSnapshot) {
    console.log("childSnapshot.key: " + userSnapshot.key);
    userSnapshot.forEach(function(gameSnapshot) {
      PrintData.innerText += gameSnapshot.key + ": " + gameSnapshot.val() +"\r";
    })
  });
});

Answer 4

请参见firebase.database.DataSnapshot

键（字符串或空值）

此DataSnapshot位置的键（路径的最后一部分）。

数据库位置中的最后一个令牌被视为其密钥。例如，“ ada”是/ users / ada /节点的键。访问任何DataSnapshot上的密钥将返回生成密钥的位置的密钥。但是，访问数据库根URL上的密钥将返回null。

// Assume we have the following data in the Database:
{
  "name": {
    "first": "Ada",
    "last": "Lovelace"
  }
}

var ref = firebase.database().ref("users/ada");
ref.once("value")
  .then(function(snapshot) {
    var key = snapshot.key; // "ada"
    var childKey = snapshot.child("name/last").key; // "last"
  });

Firebase Web-是否可以获取值的名称？

4 个答案: