AngularFire custom order by ranking - angularjs

Question

I'm trying to sort teams by ranking, using AngularFire and Firebase.
In Firebase I have 4 teams where I store only the name.
I also store matches, which have a reference to both teams disputing that match and the score for each one.
The matches node looks like this:
matches
-KQgphN_5692GySN0Oxz
home_team: teamA
away_team: teamB
score
home: 1
away: 2
-KQlu6XLak6LgAr9cTty
home_team: teamC
away_team: teamD
score
home: 2
away: 2
And the teams node:
teams
teamA
name: "Team A"
teamB
name: "Team B"
teamC
name: "Team C"
teamD
name: "Team D"
So, I need to order these teams by vitories, draws and losses by watching the results in realtime.
I have a ng-repeat that lists teams like this:
<li ng-repeat="team in teams">{{team.name}}</li>
So, how can I order these teams by wins, taking in account that a win is equivalent to 3 points, a draw is 1 point and a loss is 0 points?
With the above matches example, the ranking should be:
1 - Team B
2 - Team C
3 - Team D
4 - Team A

Answer 1

You can order a Firebase Database query by a nested value, as long as that nested value is at a fixed path. This means you'll need to store the score for each team, e.g.
teams
teamA
name: "Team A"
score: 20
teamB
name: "Team B"
score: 12
teamC
name: "Team C"
score: 42
teamD
name: "Team D"
score: 31
With this structure, you can load the top teams in order with:
var leaders = ref.child('teams').orderByChild('score').limitToLast(3);
leaders.on('value', function(snapshot) {
leaders.forEach(function(leaderSnapshot) {
console.log(leaderSnapshot.child('name').val());
});
});
This will print:
Team A
Team D
Team C
So to get the leaderboard, you'll need to invert them.