Firebase.ServerValue.TIMESTAMP not synched between listeners and the client that actually adds data

Question

Here is the simplest example possible:

var fb = new Firebase(\'https://xxxxxxxxxxx.firebaseio.com/test\');

fb.limitToLast(1).on(\'child_added\', function(sn         


        

Answer 1

Firebase fires two local events for that write operation:

1. it immediately fires a child_added event with the local timestamp (corrected for your expected offset to the server)
2. it later fires a child_changed event with the actual timestamp as the server specified it.

So you can solve the problem by listening for both events:

var fb = new Firebase('https://xxxxxxxxxxx.firebaseio.com/test');

var query = fb.limitToLast(1);
query.on('child_added', function(snap) {
    console.log('key', snap.key());
    console.log('val', snap.val());
});
query.on('child_changed', function(snap) {
    console.log('key', snap.key());
    console.log('val', snap.val());
});

fb.push({
    date_now: Firebase.ServerValue.TIMESTAMP
});

In general it is recommended to handle all child_* events and not just child_added. There may be more reasons why the server has to update or remove the value, to correct for the local event.

If you prefer having a single callback/event handler, you can also listen for the value event:

var query = fb.limitToLast(1);
query.on('value', function(snap) {
    snap.forEach(function(child) {
        console.log('key', child.key());
        console.log('val', child.val());
    });
});

You'll note the use of forEach() in the callback.