Mongoose Filter & Sort Array of Objects Using Aggregate

Question

i'm new in Nodejs and Mongodb. I have schema like this:

var x= new Schema({
        title: string,
        articles: [{
            article_date: Date    
            seq: Number
        }]
    }),
Book = mongoose.model('Book', orderSchema);

I have data like this:

{
  title: "a",
  articles: [
    {article_dt: "2023-05-09T00:00:00.000+00:00", seq:1},
    {article_dt: "2021-12-31T00:00:00.000+00:00", seq:2},
    {article_dt: "2022-12-31T00:00:00.000+00:00", seq:3}
  ]
}

I want to show the data based on parameter article_date and sort article_date desc.

I've tried this and i can filter the data based on parameter

let paramDate: Date
Book.aggregate([{
    $project:{
        articles:{
            $filter:{
                input: '$articles',
                    as: 'art',
                        cond: {$lt: ['$$art.article_dt', paramDate]}
            }
        }
    }
}])

But i dont know how to sort the array. I want to sort desc. I've tried this https://www.mongodb.com/docs/manual/reference/operator/aggregation/sortArray/ but it wont work..

I'm using: Mongoose 6.11.1 Node 16.16.0 Mongodb 5.0.9

Please help

Answer 1

db.collection.aggregate([
  {
    $project: {
      articles: {
        $filter: {
          input: "$articles",
          as: "art",
          cond: {
            $lt: [
              "$$art.article_dt",
              "2023-01-01T00:00:00.000+00:00"
            ]
          }
        }
      }
    }
  },
  {
    "$unwind": "$articles"
  },
  {
    "$sort": {
      "articles.article_dt": 1
    }
  },
  {
    "$group": {
      "_id": "$_id",
      "articles": {
        "$push": {
          article_dt: "$articles.article_dt",
          seq: "$articles.seq"
        }
      }
    }
  }
])

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