Question

在.on方法完成后，如何在我的firebase中循环所有项目并递增所有值后，如何打印“obj”值？简而言之，我在这里要做的是，一旦循环完成，我想将结果（“obj”）打印到控制台。

在此欣赏任何帮助！感谢。

var obj = {
    "20120101" : {"neutral": 0, "positive": 1, "negative": 2},
    "20120101" : {"neutral": 0, "positive": 1, "negative": 2}
} //above is just an example on the structure of the object

var fbase = new Firebase("https://<appname>.firebaseio.com/");
fbase.on('child_added', function(snapshot){
    var item = snapshot.val(); //has the attributes of: date & classification
    var date_str = item.date;
    if (!obj[date_str]){
        //initialise the counting;
        obj[date_str] = { "negative": 0, "neutral": 0, "positive" : 0 };
    }
    obj[date_str][item.classification] += 1;
});
console.log(obj);

Answer 1

在咨询Firebase文档后，我终于找到了我的问题的答案： https://www.firebase.com/docs/javascript/datasnapshot/index.html

以下是我更新的代码，以防有人遇到同样的问题：

var obj = {
    "20120101" : {"neutral": 0, "positive": 1, "negative": 2},
    "20120101" : {"neutral": 0, "positive": 1, "negative": 2}
} //above is just an example on the structure of the object

var fbase = new Firebase("https://<appname>.firebaseio.com/");
fbase.once('value', function(allMessagesSnapshot) {
    allMessagesSnapshot.forEach(function(messageSnapshot) {
        var date = messageSnapshot.child('date').val();
        var classification = messageSnapshot.child('classification').val();
        // Do something with message.
        if (!obj[date]){
            obj[date] = { "negative": 0, "neutral": 0, "positive" : 0 };
        }
        obj[date][classification] += 1;
    });
    console.log(obj);
});

感谢您的回答，感激不尽！：d

Answer 2

你必须把它放在回调中：

var obj = {
    "20120101" : {"neutral": 0, "positive": 1, "negative": 2},
    "20120101" : {"neutral": 0, "positive": 1, "negative": 2}
} //above is just an example on the structure of the object

var fbase = new Firebase("https://<appname>.firebaseio.com/");
fbase.on('child_added', function(snapshot){
    var item = snapshot.val(); //has the attributes of: date & classification
    var date_str = item.date;
    if (!obj[date_str]){
        //initialise the counting;
        obj[date_str] = { "negative": 0, "neutral": 0, "positive" : 0 };
    }
    obj[date_str][item.classification] += 1;
    console.log(obj);
});

因为回调是在将来的某个时间调用的，所以数据唯一可用的位置是回调内或可以从回调中调用的任何函数。

如何在回调函数之后访问和打印JSON对象值

2 个答案: