mongodb push if key exists otherwise set array - node.js

Question

If the Investment has deletedDocuments key exists, push the new item to the array, it works fine but
if the deletedDocuments key does not exist in Investment I want to set the item as array, but its setting a [] blank array in db, item values are not saved
const deletedDoc = {
_id: updatedInvestment.id,
docType: 'CADocument',
deletedBy: user,
deletedDate: new Date()
}
if (updatedInvestment.deletedDocuments && updatedInvestment.deletedDocuments.length) {
await Investment.updateOne(
{ "_id": updatedInvestment._id },
{ $push: { "deletedDocuments": deletedDoc } }
);
// this works fine
} else {
await Investment.updateOne(
{ "_id": updatedInvestment._id },
{ $set: { "deletedDocuments": [deletedDoc] } }
// this is setting a blank array [] in the db
);
}

Answer 1

I am thinking about two options here:
Using not in in the filter + push to add the deleted doc to the array.
Using the $addToSet operator.
1:
If you have defined deletedDocuments as an array of objects in your schema you could do something like the following:
await Investment.updateOne(
{
"_id": updatedInvestment._id,
// I'm supposing your deletedDocuments have an _id here
"deletedDocuments._id": { $nin: [deletedDoc._id] }
},
{ $push: { "deletedDocuments": deletedDoc } }
);
This will filter if the deletedDoc does not already exists, if it not, it will push it to the array.
2:
If you have defined deletedDocs as an array of docs ObjectIds instead of objects, you could use the $addToSet operator.
The $addToSet operator adds a value to an array unless the value is already present, in which case $addToSet does nothing to that array.
await Investment.updateOne(
{
"_id": updatedInvestment._id,
},
// Be carefull here, you have to "insert" the deletedDoc's _id if your schema is an ObjectId array
{ $addToSet: { "deletedDocuments": deletedDoc._id } }
);
$addToSet mongodb docs
Not In mongodb docs