mongodb insert then conditional sum followed by updating sum to another collection - mongodb

Question

I am trying to
insert a new record with a points field in to reputationActivity collection
get sum of points from reputationActivity collection where user id matches
insert the resulting sum to users collection
Here is mongo playground which does not work right now - https://mongoplayground.net/p/tHgPpODjD6j
await req.db.collection('reputationActivity').insertOne({
_id: nanoid(),
"userId": userId,//insert a new record for this user
"points": points,//insert integer points
},
function(){
req.db.collection('reputationActivity').aggregate([ { $match: { userId: userId } },
{ TotalSum: { $sum: "$points" } } ]); // sum of point for this user
req.db.collection('users').updateOne(
{_id: userId},
{$set: {"userTotalPoints": TotalSum}},// set sum in users collection
)
}
)
});
The above code gives me an error that Total sum is not defined. Is it better to do this without a callback function and if so, how?

Answer 1

write in one single block of command, use drop command carefully. it's used here to show start to end and illustration purposes only.
> db.reputation.drop();
true
> db.reputation.insertOne(
... {_id: 189, "userId": 122, "points": 60});
{ "acknowledged" : true, "insertedId" : 189 }
> var v_userId = 122;
> db.reputation.aggregate([
... {
... $match: {
... userId: v_userId
... }
... },
... {
... $group: {
... "_id": null, "TotalSum": {$sum: "$points"}}
... },
... ]).forEach(function(doc)
... {print("TotalSum: " +doc.TotalSum,
... "userId: " +v_userId);
... db.users.updateOne(
... {"userId":v_userId}, {$set:{"userPoints":doc.TotalSum}});
... }
... );
TotalSum: 60 userId: 122
> db.users.find();
{ "_id" : 189, "userId" : 122, "points" : 60, "userPoints" : 60 }
>