Retrieve value from mongoose object after query - node.js

Question

I have a query as follows :
await Categories.findOne({slug : _gender} , { _id : 0 , categories :{$elemMatch : {slug : _mainCategory}}})
and the model is this :
const categoriesSchema = mongoose.Schema({
_id: mongoose.Schema.Types.ObjectId,
title: { type: String },
slug: { type: String }, ==> match first param with this
categories: [
{
_id: mongoose.Schema.Types.ObjectId,
title: { type: String },
slug: { type: String }, ==> match the second param with this
categories: [ ==> retrieve this field
{
_id: mongoose.Schema.Types.ObjectId,
title: { type: String },
slug: { type: String },
},
],
},
],
});
_gender and _mainCategory are params.
The output it gives is as follows:
{
"categories": [
{
"id": "12",
"title": "Ayakkabı",
"slug": "kadin-ayakkabi", // ==> this is the { _id : 0 , categories :{$elemMatch : {slug : _mainCategory}} part, one level above this is the part which matches the {slug : _gender}
"image": "https://webizade.com/bm/img/",
"categories": [ // ===> this is the value I want to retrieve after the query
{
"id": "100",
"title": "Topuklu Ayakkabı",
"filter_title": "ayakkabi",
"slug": "kadin-topuklu-ayakkabi-x-g1-c107",
"image": "https://webizade.com/bm/img/"
},
{
"id": "101",
"title": "Spor Ayakkabı",
"filter_title": "ayakkabi",
"slug": "spor-ayakkabi",
"image": "https://webizade.com/bm/img/"
},
{
"id": "102",
"title": "Günlük Ayakkabı",
"filter_title": "ayakkabi",
"slug": "kadin-gunluk-ayakkabi-x-g1-c1352",
"image": "https://webizade.com/bm/img/"
},
{
"id": "103",
"title": "Babet",
"filter_title": "ayakkabi",
"slug": "kadin-babet-x-g1-c113",
"image": "https://webizade.com/bm/img/"
},
{
"id": "104",
"title": "Sandalet",
"filter_title": "ayakkabi",
"slug": "kadin-sandalet-x-g1-c111",
"image": "https://webizade.com/bm/img/"
},
{
"id": "105",
"title": "Terlik",
"filter_title": "ayakkabi",
"slug": "kadin-terlik-x-g1-c110",
"image": "https://webizade.com/bm/img/"
},
{
"id": "144",
"title": "Kar Botu",
"filter_title": "ayakkabi",
"slug": "kar-botu",
"image": "https://webizade.com/bm/img/"
}
]
}
]
}
As far as matching the correct object goes, this is correct. However, I want to retrieve the "categories" array inside the outer categories array after finding the correct object. But I don't know the correct syntax for doing that.
Appreciate any help.