How to Implement SUM() function of SQL in cloud Firestore

Question

I am storing scores of a user in google cloud firestore as each score a new document in the collection named as \"points\".

collection name: points

Answer 1

You can either use forEach or iterate in a for loop. This answer on stack overflow could help. Here's an example from the same:

for (var i in querySnapshot.docs) {
    const doc = querySnapshot.docs[i]
    //do what you want to here
}

---OR---

you can use forEach like this

 const collRef = firebase.firestore().collection('todos');
  const query = collRef.orderBy('position');
  const items = query.get()
    .then((snapshot) => {
      let newCount = 0;
      snapshot.forEach((doc) => {
        const docRef = collRef.doc(doc.id);
        docRef.update({ position: newCount });
        newCount += 1;
      });
    });