// Get a new write batch
        const batch = writeBatch(db);

        var TransactionRecordRef = db.collection("TopUpRecord").doc();
        batch.set(TransactionRecordRef, {
            Amount: FinalTopUpAmount,
            DateTime: serverTimestamp(),
            StudentID: StudentID,
        });
               

        var TopUptoUserRef = db.collection("user").doc(UserID);
        batch.update(TopUptoUserRef, { "studentAmount": UserTotalAmount });

        batch.commit();

Hi, the above is my code that needs to use write batch to create a new document on TopUpRecord and update the user's amount. Now I have two questions that I need to ask one is how can I know whether the batch successfully updates the record to the firestorm and I also found that my above code has an error which "db. the collection is not a function" Is anyone why this issue happened?