Firebase: How To Get The Data When Child_added Complete

I have a case when I need to fetch all event objects. Each event object has a property city_id which is a relationship key to a single city object from the list with all cities. ..

Solution 1:

The only way to know when loading of the initial data is done is to use a value event. I haven't really used async/await yet, but expect you'll need something like this:

async function getAllEvents() {
    const eventsRef = rootRef.child('events');
    const eventsArray = [];

    await eventsRef.on('value', async (snapshot) => {
      snapshot.foreach(function(child) {
        const eventObject = child.val();
        const cityObject = await getEventCity(eventObject.city_id);
        eventObject.city = cityObject;
        eventsArray.push(eventObject);
      });
    });

    return eventsArray;
}