javascript - callback called even after off? -

i have situation if call off on reference keeps calling callbacks?

var ref = new firebase('https://stackoverflow.firebaseio.com/31069762');  (var n = 0; n < 1024; ++n) {   ref.push(n) }  ref.on('child_added', function(snapshot) {   if (snapshot.val() > 10) {      console.log('off') // printed multiple times.      ref.off();   } }); 

when call off() stop firebase client firing child_added events new data comes in. not prevent firing child_added events data client received.

you can interesting behavior way. example, snippet:

var ref = new firebase('https://stackoverflow.firebaseio.com/31069762'); ref.remove();  (var n = 0; n < 1024; ++n) {   ref.push(n) }  ref.on('child_added', function(snapshot) {   console.log(snapshot.val());   if (snapshot.val() > 10) {      console.log('off') // printed multiple times.      ref.off();   } }); 

will print:

1 2 . . . 11 "off" 12 "off" . . . 1024 "off" 

the data ref download "one initial packet" when register listener , there on child_added events fired.

now let's change code around:

var ref = new firebase('https://stackoverflow.firebaseio.com/31069762'); ref.remove();  ref.on('child_added', function(snapshot) {   console.log(snapshot.val());   if (snapshot.val() > 10) {      console.log('off') // printed multiple times.      ref.off();   } });  (var n = 0; n < 1024; ++n) {   ref.push(n) } 

so in case first register listener , start pushing values. output:

1 2 . . . 11 "off" 

so ordering stops straight away. since started listening child_added before there data, initial payload empty , each child after separate update.

note depends on internals of firebase client , haven't checked how works there. "one initial packet" mentioned above how i visualize it.

if don't want process data after 10, there 2 solutions can think off.

1. the 1 do: keep local "i done" flag

2. use query limit data firebase downloads, instead of filtering client side:

   ref.orderbyvalue().endat(10).on('child_added'... 

   note orderbyvalue introduced in version 2.2.7 of firebase javascript sdk. took me while figure out why couldn't use in jsbin. :-/