How to query the existing children and loop over an Object to detect if it exists in Firebase using a Google Cloud Function?

Question

I am trying to update (adding) some children on a firebase database. On this scenario I need to update a node without overwriting all the child nodes with Google Cloud Function using an update Object.

This question derives from this one here: How to update a node without overwriting all the child nodes with Google Cloud Function using a update Object?

My data structure is like this:

root: { 
  doors: {
    111111111111: {
       MACaddress: "111111111111",
       inRoom: "-LBMH_8KHf_N9CvLqhzU", // I will need this value for the clone's path
       ins: {
          // I am creating several "key: pair"s here, something like:
          1525104151100: true,
          1525104151183: true,
       }
    },
    222222222222: {
       MACaddress: "222222222222",
       inRoom: "-LBMH_8KHf_N9CvLqhzU", // I will need this value for the clone's path
       ins: {
          // I am creating several "key: pair"s here, something like:
          2525104157710: true,
          2525104157711: true,
       }
    }
  },
  rooms: {
    -LBMH_8KHf_N9CvLqhzU: {
      ins: {
        // I want the function to clone the same data here:
        1525104151100: true,
        1525104151183: true,
      }
    }
  }

I am trying to to query the existing "ins" and loop over the object to detect if it exists before I add them so I can add a suffix to the key in case they are already there. This is my function ate the moment.

 exports.updateBuildingsOuts = functions.database.ref('/doors/{MACaddress}').onWrite((change, context) => {
    const afterData = change.after.val(); // data after the write

    const roomPushKey = afterData.inRoom;
    const ins = afterData.ins;

    const updates = {};
    // forEach loop to update the keys individually
    Object.keys(ins).forEach(key => {
            parentPath =  ['/rooms/' + roomPushKey + '/ins/']; // defining the path where I want to check if the data exists
            // querying the "ins"
            admin.database().ref().parentPath.on('value', function(snapshot) {
                if (snapshot.hasChild(key)) {
                    updates['/rooms/' + roomPushKey + '/ins/' + key + "_a"] = true; // define 'updates' Object adding a suffix "_a"

                    return admin.database().ref().update(updates); // do the update adding the suffix "_a"

                } else {
                    updates['/rooms/' + roomPushKey + '/ins/' + key] = true; // define update Object without suffix

                    return admin.database().ref().update(updates); // do the 'updates' without suffix
                }
              });
        });   

This cloud function is retrieving an Error:

TypeError: Cannot read property 'on' of undefined at Object.keys.forEach.key

I am sure I overcomplicating but I haven't been able to find a cleaner logic for this.

Would you have any suggestions on how to do this leanly? Is it possible?

Answer 1

You could do as follow:

let afterIns;
exports.updateRoom = functions.database.ref('/doors/{MACaddress}').onWrite((change, context) => {

    const beforeData = change.before.val();  //data before
    const insBefore = beforeData.ins;

    const afterData = change.after.val(); // data after the write
    const roomPushKey = afterData.inRoom;
    afterIns = afterData.ins;

    return admin.database().ref().update(updates);

    const updates = {};

    Object.keys(ins).forEach(key => {
        if (insBefore.hasOwnProperty(key)) { // checking if the insBefore object has a key equal to value 'key'
            //True -> add an extra character at the existing key
            updates['/rooms/' + roomPushKey + '/ins/' + key + '_a'] = true;  //<- _a being the extra character
        } else {
            updates['/rooms/' + roomPushKey + '/ins/' + key] = true;
        }
    });

    return admin.database().ref().update(updates);

}).catch(error => {
    console.log(error);
    //+ other error treatment if necessary

});

Don't forget the function returns the data before change.before.val(); (in addition to the data after), therefore you don't have to do admin.database().ref().parentPath.on('value', function(snapshot) {

---

EDIT after comments

This should work, but I haven't test it. You may need to test is insBefore is undefined in addition to testing it is null. I let you fine tune it.

let insAfter;
let roomPushKey ;
exports.updateRoomIns = functions.database.ref('/doors/{MACaddress}').onWrite((change, context) => {
    const afterData = change.after.val(); // data after the write
    roomPushKey = afterData.inRoom;
    insAfter = afterData.ins;
    return admin.database().ref('/rooms/' + roomPushKey).once('value').then(snapshot => {
    const insBefore = snapshot.val().ins;
    const updates = {};
    if (insBefore === null || insBefore === undefined ) {
        Object.keys(insAfter).forEach(key => {
           updates['/rooms/' + roomPushKey + '/ins/' + key] = true;
        });
    } else {
        Object.keys(insAfter).forEach(key => {
           if (insBefore.hasOwnProperty(key)) {
              updates['/rooms/' + roomPushKey + '/ins/' + key + '_a'] = true; 
           } else {
              updates['/rooms/' + roomPushKey + '/ins/' + key] = true;
           }
        });
    }
    return admin.database().ref().update(updates);
    });
});.catch(error => {
    console.log(error);
    //+ other error treatment if necessary

});