Sorting the Firebase snapshot before setting values to state

Question

I am getting values from Firebase, since Firebase do not support combining multiple orderByChild() , I guess we have to sort the values at client side

The Firebase query is

componentDidMount() {
    const device_id = DeviceInfo.getUniqueID();
    this.codesRef = firebase.database().ref(`codes`).orderByChild('owner').equalTo(device_id);
    this.codesRef.keepSynced(true);
    this.codesRef.on('value', this.handleCodesUpdate);
}

componentWillUnmount() {
    this.codesRef.off('value', this.handleCodesUpdate);
}

handleCodesUpdate(snapshot) {
    if (snapshot.val()) {

        //sort the snapshot before assigning to state

        this.setState({ codes: snapshot.val() });
    }
    else {
        this.setState({ codes: {} });
    }
}

the firebase response

{ 
   "-L1SI6Ceu2mPCxDU89NH":{  
      "status":0,
      "purchase_date":1514467520472,
      "title":"Mnic Htod",
      "start_in":0,
      "owner":"fgdgfdgdfgdfgdfgdfg",
      "valid_duration":1,
      "createdAt":"2017-11-28 18:55:20",
      "code":"218688"
   },
   "-L1SI3krvOYDaqr8g_cs":{  
      "status":0,
      "purchase_date":1514467510437,
      "title":"Banfog",
      "start_in":0,
      "owner":"xgdfgdfgdfgfdgdf",
      "valid_duration":1,
      "createdAt":"2017-11-28 18:55:10",
      "code":"804452"
   },
   "-L1SI1eFHX7a0_RFhZtW":{  
      "status":0,
      "purchase_date":1514467501822,
      "title":"Blizaard",
      "start_in":0,
      "owner":"xcvxcvxcvxcvxcv",
      "valid_duration":1,
      "createdAt":"2017-11-28 18:55:1",
      "code":"300149"
   }
}

I want to sort the data by createdAt

Looking forward for much needed help

Thank you

Answer 1

The simplest way is with a snippet like this:

var sortedKeys = Object.keys(json).sort(function(a,b) { 
  return json[b].createdAt < json[a].createdAt 
});

See this runnable version:

 var json = { "-L1SI6Ceu2mPCxDU89NH":{ "status":0, "purchase_date":1514467520472, "title":"Mnic Htod", "start_in":0, "owner":"fgdgfdgdfgdfgdfgdfg", "valid_duration":1, "createdAt":"2017-11-28 18:55:20", "code":"218688" }, "-L1SI3krvOYDaqr8g_cs":{ "status":0, "purchase_date":1514467510437, "title":"Banfog", "start_in":0, "owner":"xgdfgdfgdfgfdgdf", "valid_duration":1, "createdAt":"2017-11-28 18:55:10", "code":"804452" }, "-L1SI1eFHX7a0_RFhZtW":{ "status":0, "purchase_date":1514467501822, "title":"Blizaard", "start_in":0, "owner":"xcvxcvxcvxcvxcv", "valid_duration":1, "createdAt":"2017-11-28 18:55:1", "code":"300149" } } var sortedKeys = Object.keys(json).sort(function(a,b) { return json[b].createdAt < json[a].createdAt }); console.log(sortedKeys); 

A few things to note:

1. You cannot get Firebase to do this operation server-side, since it can only order/filter on a single property. See http://stackoverflow.com/questions/26700924/query-based-on-multiple-where-clauses-in-firebase .
2. You're throwing the order information that Firebase returns for the data away when you call snapshot.val() . I don't think that's a problem here, but if you want to maintain that ordering, use snapshot.forEach() to loop over the results. See orderByChild not working in Firebase .
3. Your date format seems flawed in the last child: "createdAt":"2017-11-28 18:55:1" . That should be "createdAt":"2017-11-28 18:55:01" to make it reliably sortable.