Is a finished callback needed for .on('xxx') event?

On my dashboard page, I am currently retrieving the top 25 comments and displaying them using the following code:

fba.orderByChild('when').limitToLast(25).on('child_added', function (d, c) { stuff });

However, the function is called for each child individually. Is there a way to trigger a callback when all the calls are completed without using a Promise to wrap the entire call?

I am considering changing this block to use .once('value') at the beginning and then attach a listener for child_added with TIMESTAMP.

Would this be the recommended approach for a situation like this?

javascriptfirebase

Answer №1

The events in Firebase related to children, such as child_, are triggered independently for each child. These events are useful for dynamically creating and updating UI elements for each child.

It's important to remember that Firebase ensures data synchronization: when a new child is added, both a child_added event and a child_removed event are triggered. This simplifies making minimal updates to the UI.

If you need to fetch all matching elements in bulk, you can use the value event:

fba.orderByChild('when')
   .limitToLast(25)
   .on('value', function (snapshot) {
       snapshot.forEach(function(child) {
           // child now represents the specific child snapshot
       });
   });

In the event that a new child is added in this scenario, the value event will retrieve all children again. This means that if you're updating a UI, the entire UI will need to be rebuilt. It's not necessarily wrong, just a different approach.

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