javascript - Firebase returns snapshot but can't access value - Stack Overflow

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Peep is always returned from the function as undefined. Can someone point me to the problem? In the success function the snapshot is returned as expected. I think it's a scoping issue.

function getPerson( id ) {

    var ref = new Firebase( "/" + id ),
    peep;

    // Attach an asynchronous callback to read the data at our people reference
    ref.once( "value", function( snapshot ) {
        //success
        peep = snapshot;

    }, function ( errorObject ) {
        //error
        //console.log( "The read failed: " + errorObject.code );
    });

    return peep;

}

Peep is always returned from the function as undefined. Can someone point me to the problem? In the success function the snapshot is returned as expected. I think it's a scoping issue.

function getPerson( id ) {

    var ref = new Firebase( "https://foo.firebaseio./people/" + id ),
    peep;

    // Attach an asynchronous callback to read the data at our people reference
    ref.once( "value", function( snapshot ) {
        //success
        peep = snapshot;

    }, function ( errorObject ) {
        //error
        //console.log( "The read failed: " + errorObject.code );
    });

    return peep;

}

• javascript
• firebase
• firebase-realtime-database

Share Improve this question Follow edited Apr 1, 2016 at 17:39 Frank van Puffelen 601k8585 gold badges890890 silver badges860860 bronze badges asked Apr 1, 2016 at 17:02 MoreScratchMoreScratch 3,08377 gold badges4040 silver badges7171 bronze badges 1

• See stackoverflow./questions/14220321/… – Frank van Puffelen Commented Apr 1, 2016 at 17:33

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3 Answers 3

Sorted by: Reset to default 5

The once() method is asynchronous that is why callback is used. You can pass a callback as a parameter to the getPerson function alongside the id.

function getPerson(id, callback) {
  var ref = new Firebase( "https://foo.firebaseio./people/" + id );

  ref.once( "value", function(snapshot) {
    var peep = snapshot;
      // error will be null, and peep will contain the snapshot
      callback(null, peep);
    }, function (error) {
      // error wil be an Object
      callback(error)
  });
}

getperson('9234342', function (err, result) {
  console.log(result);
});

Yes it should be because the success callback is not fired immediately. It receives data then get into it.

Try returning the peep inside the callback like.

return ref.once( "value", function( snapshot ) {
        //success
        peep = snapshot;
        return peep;

    }, function ( errorObject ) {
        //error
        //console.log( "The read failed: " + errorObject.code );
    });

Hope it helps.

The once() method is asynchronous which is why a callback is used. You are returning peep before it even has a value. You need to return peep after it is defined in the callback.

function getPerson( id ) {

    var ref = new Firebase( "https://foo.firebaseio./people/" + id ),
    peep;

    // Attach an asynchronous callback to read the data at our people reference
    return ref.once( "value", function( snapshot ) {
        //success
        peep = snapshot;
        return peep;
    }, function ( errorObject ) {
        //error
        //console.log( "The read failed: " + errorObject.code );
    });
}

And then use it like this:

getPerson('9234342').then(function(snapshot) {
  console.log(snapshot.val());
}).catch(function(error) {
  console.error(error);
});

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