Mongo Mongoose - How to dynamically pick the value for $in operator inside a condition?

Question

I am ierating through an object with key value pairs, where the value is an array of objects. If certain prop (lets say title) is already in the db, I do not want to save that object containing same title. When I hard code the title as a string, it works fine If I pass a map iteration to $in, nothing works (the objects are being saved in all cases then). What am I doing wrong?

 for (let key in reports) {
            const condition = reports[key].map((x) => {
                return x.title;
            });
            await Product.findOneAndUpdate({
                    "name": key
                },
                [
                    {
                        "$set": {
                            "reports": {
                                "$cond": [
                                    {
                                        "$in": [
                                            //this works as expected:
                                            "IAmProduct1",
                                            "$reports.title"

                                            //this does Not work when iterating:
                                            // condition,
                                            // "$reports.title"
                                        ]
                                    },
                                    "$reports",
                                    {
                                        "$concatArrays": [
                                            "$reports",
                                            reports[key]
                                        ]
                                    }
                                ]
                            }
                        }
                    }
                ], {new: true}) 
         }

Answer 1

Function reports[key].map((x) => { return x.title; }) (or just reports[key].map(x => x.title)) returns an array rather than a string:

const reports = { key1: [{ title: "IAmProduct1" }] };

print(reports['key1'].map(x => x.title));

-> [ 'IAmProduct1' ]

Which is not

'IAmProduct1'

Maybe $setUnion would be simpler:

Product.findOneAndUpdate(
   { "name": key },
   [
      {
         $set: {
            reports: { $setUnion: ["$reports", reports[key]] }
         }
      }
   ]
)

Or put the condition in your filter, should be much more efficient:

Product.findOneAndUpdate(
   { "name": key, "reports.title": {$ne: condition } },
   [
      {
         "$set": {
            "reports": {
               "$concatArrays": [
                  "$reports",
                  reports[key]
               ]
            }
         }
      }
   ],
   { new: true }
)