How do you delete a certain id from a document in mongoose? Edit: Why didn't this work (see edit) - mongodb

Question

So I have this kind-a-like schema at the moment
user:{ _id: string,
shifts:[_id:string],
name: ... ,
...
}
And now I want to delete a shift._id from all my users who have this.
I allready have an array of all the users their id's who have this shift._id.
I've tried this, with shift_id as the id of the shift i want to delete:
userIdArray.forEach(user_id => {
UserSchema.update({_id: user_id}, {$pull: {shifts: shift_id} });
});
and got the error:
UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at ServerResponse.setHeader (_http_outgoing.js:535:11)
Can somebody explain me what I did wrong?
Edit:
So what i did was, i called a function named:
function deleteShiftIdInUsers(users, shift_id){
users.forEach(user_id => {
UserSchema.update({_id: user_id}, {$pull: {shifts: shift_id} });
});}
and called this function in my async (req, res, next) route.
Now i just execute this code within the async function instead doing it like code...;
deleteShiftIdInUsers(users, shift_id);
res.status(200).json(...);
still new to js, so what did i do wrong?

Answer 1

I think, You need to call the mongoose function with async/await, you should use updateMany with $in instead of looping for user_id
var ObjectId = require("mongoose").Types.ObjectId
async function deleteShiftIdInUsers(users, shift_id){
users = users.map(user_id => ObjectId(user_id))
return await UserSchema.updateMany({"_id": {"$in": users}}, {"$pull": {"shifts": ObjectId(shift_id)} });
}
when you are calling this function
await deleteShiftIdInUsers(users, shift_id);
res.status(200).json(...);