Mongoose call a function for a field when inserting a document

Question

Below code snippet is working fine.

function simple() {
  return 10000;
}

db.Invoice.create({
  items: selectedItems,
  _id: simple("userid")
});

But if I change simple function to this

async function getNextSequence(sequenceName) {
  const sequenceDocument = await db.Counter.findOneAndUpdate(
    { _id: sequenceName },
    { $inc: { seq: 1 } },
    { new: true }
  );

  console.log("seq", sequenceDocument);

  return sequenceDocument.seq;
}

db.Invoice.create({
  items: selectedItems,
  _id: getNextSequence("userid")
});

This gives me an error.

ValidationError: Invoice validation failed: _id: Cast to Number failed for value "Promise { }" at path "_id"

Why could this happen?

Answer 1

getNextSequence is an asynchronous function which needs to be awaited - otherwise you're trying to save Promise to your MongoDB which is not supported. Try:

db.Invoice.create({
    items: selectedItems, 
    _id: await getNextSequence('userid'),
})