MongoDB lookup N:M

mongodb_lookup_n_to_m.js

// Orders collection
{
  "_id" : ObjectId("634312b873d381100e27b8ea"),
    "company" : "Microsoft",
      "products" : [
        ObjectId("634312f073d381100e27b8ec"),
        ObjectId("634312f073d381100e27b8ed")
      ]
},
{
  "_id" : ObjectId("634312b873d381100e27b8eb"),
    "company" : "Apple",
      "products" : [
        ObjectId("634312f073d381100e27b8ed")
      ]
}
// Products collection
{
  "_id" : ObjectId("634312f073d381100e27b8ec"),
    "name" : "Mouse logitech",
      "orders" : [
        ObjectId("634312b873d381100e27b8ea")
      ]
},
{
  "_id" : ObjectId("634312f073d381100e27b8ed"),
    "name" : "Keyboard logitech",
      "orders" : [
        ObjectId("634312b873d381100e27b8ea"),
        ObjectId("634312b873d381100e27b8eb")
      ]
}
// Query( can be queried from both endsm the example only products )
db.getCollection("products").aggregate({
  $lookup: {
    from: "orders",
    localField: "orders",
    foreignField: "_id",
    as: "orders"
  }
}
)
// Result
{
  "_id" : ObjectId("634312f073d381100e27b8ec"),
    "name" : "Mouse logitech",
      "orders" : [{
        "_id": ObjectId("634312b873d381100e27b8ea"),
        "company": "Microsoft",
        "products": [
          ObjectId("634312f073d381100e27b8ec"),
          ObjectId("634312f073d381100e27b8ed")
        ]
      }
      ]
},
{
  "_id" : ObjectId("634312f073d381100e27b8ed"),
    "name" : "Keyboard logitech",
      "orders" : [{
        "_id": ObjectId("634312b873d381100e27b8ea"),
        "company": "Microsoft",
        "products": [
          ObjectId("634312f073d381100e27b8ec"),
          ObjectId("634312f073d381100e27b8ed")
        ]
      },
      {
        "_id": ObjectId("634312b873d381100e27b8eb"),
        "company": "Apple",
        "products": [
          ObjectId("634312f073d381100e27b8ed")
        ]
      }
      ]
}