Clever Geek Handbook

How to know when a Firebase request has ended

I want to collect the last 10 items from my datastore. I suppose I should be able to do this with .child()

and .limitToLast()

, which emits an event every time a result is added to the child.

I don't necessarily know if there are only 10 items, so a simple counter won't work.

How do I know when Firebase has finished producing results?

Sample search code:

var plots = [];
firebaseDatastore.child("plots").orderByChild("unicode-timestamp").limitToLast(10).on("child_added", function(snapshot) {
    // Add the new item to the list
    plots.push(snapshot.val());
});

I need to know when the last graph was added, whether or not it reached the limit.

+3


source to share


1 answer


Firebase request never ends. It keeps tracking (in your case) the graphs by unicode-timestamp and keeps a "window" of the last 10 graphs.

So:

  • child_added: timestamp1
  • child_added: timestamp2
  • ...
  • child_added: timestamp9
  • child_added: timestamp10

And then when you add another plot:



  • child_removed: timestamp1
  • child_added: timestamp11

If you are not going to use this behavior, you have two options:

  • use event value

    and then snapshot.forEach

    over child nodes
  • save the counter and off

    your listener when you reach the number of babies you expect.
+2


source






More articles:


All Articles