How to add child to a List in Firebase Realtime Database with a cloud function?

Question

I try to create a Firebase cloud function that react on new "Event" in the realtime database and add a "notification" object in a notification list for the corresponding users. i succeed to get new event information,to push a notification a corresponding users but not in a list format (but in hashmap format).

So I tried to get the numbers of children in order to push new notification with the good index. I don't know how to manage promises in that case.

The idea is to get sport_name and level from the new event, to get corresponding users in Sport and add notification for each users.

• There is my cloud function :

  exports.detectEvent = functions.database
  .ref("Event/{eventID}")
  .onCreate((snapshot, context) => {
      const event = snapshot.val();
      const sport = event.sport.name;
      const level = event.niveau;
      const name = event.name;
      var promises=[];
      var path = "Sports/" + sport + "/" + level;
      var notif = {
          type : "Event",
          contentID : context.params.eventID,
          message : sport + " : Un nouvel événement vous correspond ! ",
          seen : false,
          date : "01"
      };
      console.log('path ', path);
      return admin.database().ref(path).once("value", function(result) {
          var datas = result.val();
          for (var property in datas)  {
              if (datas.hasOwnProperty(property)) {
                  promises.push(admin.database().ref("Users/"+datas[property]+"/notifications").on("value", function(snapshot) {
                      console.log("There are "+snapshot.numChildren()+" notifs");
                      admin.database().ref("Users/"+datas[property]+"/notifications").child(snapshot.numChildren()).set(notif)
                    }));
  
  
          }
  
      }
      return Promise.all(promises);
  })
  

  });

• There is the table :

Table

Answer 1

This code works but it create a random key for notifications. How to put integer (0,1,2,...) as key in order to have a list in my database ?

<pre>
exports.detectEvent = functions.database
.ref("Event/{eventID}")
.onCreate((snapshot, context) => {
    const event = snapshot.val();
    const sport = event.sport.name;
    const level = event.niveau;
    const name = event.name;
    var promises=[];
    var path = "Sports/" + sport + "/" + level;
    var notif = {
        type : "Event",
        contentID : context.params.eventID,
        message : sport + " : Un nouvel événement vous correspond ! ",
        seen : false,
        date : "01"
    };
    console.log('path ', path);
    return admin.database().ref(path).once("value", function(result) {
        var datas = result.val();
        for (var property in datas)  {
            if (datas.hasOwnProperty(property)) {
                promises.push(admin.database().ref("Users/"+datas[property]+"/notifications").push(notif));
            }

        }
        return Promise.all(promises);
    })
});

<code>