Unable to parse the snapshot of Firebase with Node.js

Question

I have an query and it returns snapshot;

ref.orderByChild("index").equalTo(currentIndex).once("value", function(snapshot) {})

When I print snapshot with ;

console.log(snapshot.val());

it is printed as follows;

{'-LBHEpgffPTQnxWIT4DI':
    {
        date: '16.05.2018',
        first: 'let me in',
        index: 1,
        second: 'let others in'
    }
},

I need to take the value date, first value of this snapshot.

I tried;

childSnapshot.val()["first"] 
childSnapshot.val()["date"] 

or

childSnapshot.child.('first') 
childSnapshot.child.('date') 

but there is no success.

Please indicate me the mistake I am doing...

My full code is as below;

var indexRef = db.ref("/LastIndex/");
var ref = db.ref("/Source/")

indexRef.on("value", function(indexSnapshot) {
    console.log(indexSnapshot.val());

    var currentIndex = indexSnapshot.val()

    ref.orderByChild("index").equalTo(currentIndex).once("value", function(snapshot) {
        console.log(snapshot.val());

        if(snapshot !== null) {
            snapshot.forEach(function (childSnapshot) {

            if(childSnapshot !== null) {
                var newRef = db.ref("/ListTest/");
                var key = newRef.push({
                    "firstLanguageWord": childSnapshot.val()["first"] ,
                    "secondLanguageWord": childSnapshot.val()["second"] ,
                    "wordType": childSnapshot.val()["type"],
                    "date": childSnapshot.val()["date"],
                    "translateType": childSnapshot.val()["transType"]
                });

                currentIndex++;
                indexRef.set(currentIndex);
            }
        });
    }
});

BR,

Erdem

Answer 1

Update, following your comments below and the update to the original question:

If it appears that your code is "iterating infinitely" it is because you use the on() method with your first query. As a matter of facts, the on() method "listens for data changes at a particular location.", as explained here .

If you just want to query once the reference, use the once() method instead. The doc is here .

---

The following is a Query , because you call the orderByChild() method on a Reference (as well as an equalTo() method).

ref.orderByChild("index").equalTo(currentIndex)

As explained here in the doc:

Even when there is only a single match for the query, the snapshot is still a list; it just contains a single item. To access the item, you need to loop over the result:

 ref.once('value', function(snapshot) { snapshot.forEach(function(childSnapshot) { var childKey = childSnapshot.key; var childData = childSnapshot.val(); // ... }); }); 

So you should do:

ref.orderByChild("index").equalTo(currentIndex).once("value", function(snapshot) {
     snapshot.forEach(function(childSnapshot) {
        console.log(childSnapshot.val().first);
        console.log(childSnapshot.val().date);      
       }); 
});