Firebase deep increment of a field in a data base

<h3>Normalizing user profiles into posts</h3>

<ul ng-controller="ctrl">
    <li ng-repeat="post in posts | orderByPriority" ng-init="user = users.$load(post.user)">
        {{user.name}}: {{post.title}}
    </li>
</ul>

var app = angular.module('app', ['firebase']);
var fb = new Firebase(URL);

app.controller('ctrl', function ($scope, $firebase, userCache) {
    $scope.posts = $firebase(fb.child('posts'));
    $scope.users = userCache(fb.child('users'));
});

app.factory('userCache', function ($firebase) {
    return function (ref) {
        var cachedUsers = {};
        cachedUsers.$load = function (id) {
            if( !cachedUsers.hasOwnProperty(id) ) {
                cachedUsers[id] = $firebase(ref.child(id));
            }
            return cachedUsers[id];
        };
        cachedUsers.$dispose = function () {
            angular.forEach(cachedUsers, function (user) {
                user.$off();
            });
        };
        return cachedUsers;
    }
});

{
    "rules" : {
        "messages" : {
            "$userId": {
                ".indexOn" : ["message", "direction"]
            }
        }
    }
}

const ref = db.ref('keyboards/SecendKeyboard/childs');
ref.on("value", function (snapshot) {
    console.log(snapshot.val());
});

const ref = db.ref('keyboards/SecendKeyboard');
ref.on("value", function (snapshot) {
    console.log(snapshot.child("childs").val());
});

const ref = db.ref('keyboards');
ref.on("value", function (snapshot) {
    snapshot.forEach(function(childSnapshot) {
        console.log(snapshot.val()); // prints StartKeyboard and SecendKeyboard
        if (snapshot.child("SecendKeyboard").exists()) {
            console.log(snapshot.child("SecendKeyboard").val());
        }
    })
});

// Change '/COLLECTION/{DOC}' to which document do you want to increment the counter when it's created
exports.counter = functions.firestore.document('/COLLECTION/{DOC}').onCreate((snap, context) => {
  const db = admin.firestore();

  // Change 'counter/ref' to where do you want to increment
  const countRef = db.doc('counter/ref');
  return db.runTransaction(t => {
    return t.get(countRef).then(doc => {
      const counter = (doc.data().counter || 0) + 1;
      t.update(countRef, {counter: counter});
    });
  });
});