mongoose - exclude embedded document from query based on condition

Question

I am using mongoose. I have the following document in my database:

question: {
    "id": "60ab9bd0d40a362189e842ff",
    "deletedAt": null
        "answers": [
        {
            "id": "60ab9e4e58a72f4768c5f63b",
            "deletedAt": "2021-05-28T20:23:30.409Z",
        },
        {
            "id": "60ab9e4e58a72f4768c5f64c",
            "deletedAt": null,
        },
    }
}

I would like to get all questions where the deletedAt field is null, as well as all answers where deletedAt field is null. So the result of my query should be this:

question: {
    "id": "60ab9bd0d40a362189e842ff",
    "deletedAt": null
        "answers": [
         {
            "id": "60ab9e4e58a72f4768c5f64c",
            "deletedAt": null,
        },
    }
}

What I have tried:

Question.aggregate([
    { $match: { deletedAt: null }},
    { $project: {
        answers: { 
          $filter: {
            input: "$answers",
            as: "answer",
            cond: { "$$answer.deletedAt": null }
          }
        }
      }
    },
    { $sort: sort },
    { $limit: limit + 1 }
]}

I would be very thankful for any kind of help!

Answer 1

use $eq operator to match condition in $filter operator,

    { $project: {
        answers: { 
          $filter: {
            input: "$answers",
            as: "answer",
            cond: { 
              $eq: ["$$answer.deletedAt", null]
            }
          }
        }
      }
    },