Javascript Firebase数据为；“未定义”；当它不是

我试图从firebase数据库中检索一些数据，但得到的值为“未定义”

这是我将数据保存到数据库的方式：

var database = firebase.database();

        database.ref().push({
        mainArray: mainArray,
        secondArray: secondArray,
        listname: listName,
        mainLanguage: mainLanguage,
        secondLanguage: secondLanguage,

  }, function(error) {
  if (error){

    stopLoader();

    showSnackbar("An error has occured! Please try again later.");
}

 var database = firebase.database().ref().child('codes');
    var codeInput = document.getElementById('mainSearch');

    database.on('value', function(snapshot) {
            if (!snapshot.hasChild(codeInput.value)) {

                codeInput.value = "";
                showSnackbar("A list with this code does not exist!<br><br>Please try another one.")
            }
            else {

               var data = snapshot.val();
               var listname = data.listname;


               console.log(listname);



            }
        });

这是我读取数据的方式，但listname的值是“未定义”：

var database = firebase.database();

        database.ref().push({
        mainArray: mainArray,
        secondArray: secondArray,
        listname: listName,
        mainLanguage: mainLanguage,
        secondLanguage: secondLanguage,

  }, function(error) {
  if (error){

    stopLoader();

    showSnackbar("An error has occured! Please try again later.");
}

 var database = firebase.database().ref().child('codes');
    var codeInput = document.getElementById('mainSearch');

    database.on('value', function(snapshot) {
            if (!snapshot.hasChild(codeInput.value)) {

                codeInput.value = "";
                showSnackbar("A list with this code does not exist!<br><br>Please try another one.")
            }
            else {

               var data = snapshot.val();
               var listname = data.listname;


               console.log(listname);



            }
        });

var-database=firebase.database（）.ref（）.child（'code'）；
var codeInput=document.getElementById（'mainSearch'）；
数据库.on（'value'，函数（快照）{
if（！snapshot.hasChild（codeInput.value））{
codeInput.value=“”；
showSnackbar（“包含此代码的列表不存在！

请尝试另一个。”）
}
否则{
var data=snapshot.val（）；
var listname=data.listname；
console.log（listname）；
}
});

这是我从数据库获得的值：

var database = firebase.database();

        database.ref().push({
        mainArray: mainArray,
        secondArray: secondArray,
        listname: listName,
        mainLanguage: mainLanguage,
        secondLanguage: secondLanguage,

  }, function(error) {
  if (error){

    stopLoader();

    showSnackbar("An error has occured! Please try again later.");
}

 var database = firebase.database().ref().child('codes');
    var codeInput = document.getElementById('mainSearch');

    database.on('value', function(snapshot) {
            if (!snapshot.hasChild(codeInput.value)) {

                codeInput.value = "";
                showSnackbar("A list with this code does not exist!<br><br>Please try another one.")
            }
            else {

               var data = snapshot.val();
               var listname = data.listname;


               console.log(listname);



            }
        });

这是数据库中数据的结构：

var database = firebase.database();

        database.ref().push({
        mainArray: mainArray,
        secondArray: secondArray,
        listname: listName,
        mainLanguage: mainLanguage,
        secondLanguage: secondLanguage,

  }, function(error) {
  if (error){

    stopLoader();

    showSnackbar("An error has occured! Please try again later.");
}

 var database = firebase.database().ref().child('codes');
    var codeInput = document.getElementById('mainSearch');

    database.on('value', function(snapshot) {
            if (!snapshot.hasChild(codeInput.value)) {

                codeInput.value = "";
                showSnackbar("A list with this code does not exist!<br><br>Please try another one.")
            }
            else {

               var data = snapshot.val();
               var listname = data.listname;


               console.log(listname);



            }
        });

---

我把代码改成了这个，现在它工作得很好。问题是我试图从错误的孩子那里得到价值。谢谢你的帮助和耐心

var database = firebase.database().ref().child('codes');
var codeInput = document.getElementById('mainSearch');


database.child(codeInput).on('value', function(snap) {

          var data = snap.val();

          var listName = data.listname;
          var mainLanguage = data.mainLanguage;
          var secondLanguage = data.secondLanguage;
          var mainArray = data.mainArray;
          var secondArray = data.secondArray;

        }); 

---

您可以设置一个jsbin来重现这个问题吗？您只是看起来缺少

var data=snapshot.val（）[codeInput]

snapshot.val（）

将返回整个

code

object@Phil我可以使用

var data=snapshot.val（）检索codes对象内部的所有内容

，但我想检索每一项并从中生成一个变量。@FrankvanPuffelen我会尝试这样做。@Magnus除了Phil的注释外，您还保存到“/”（数据库的根目录），但从/code检索/