expressjs - mongoDb 返回嵌套子数组

Question

im trying to create a seprate route in my api for a subArray from a nested array. using expressJs.

categories array:

const Categories = [
{
    _id: 's654fs54s6d4f'
    title: 'category 1',
    SubCats: [
        {
            _id: 'jhgfsf68746'
            name: 'subcat 1',
            image: '/assets/images/vr-box-6203301_1920.jpg',
        },
        {
            _id: 'vb40n5b4vn'
            name: 'subcat 2',
            image: '/assets/images/galaxy-s20_highlights_kv_00.jpg',
        },
    ]
},
]

categoryModel:

import mongoose from 'mongoose'

const Catschema = mongoose.Schema({
    name: {
        type: String,
        required: true,
    },
    image: {
        type: String,
        required: true,
    },
})

const CategorySchema = mongoose.Schema(
    {
        title: {
            type: String,
            required: true,
        },
        SubCats: [Catschema]
    },
    {
        timestamps: true,
    }
)

const Category = mongoose.model('Category', CategorySchema)

export default Category

categoryController:

this would return the whole array

const getCategories = asyncHandler(async (req, res) => {
   const categories = await Category.find({})
   res.json(categories)
})

i want to return 'SubCats' array.

tried this but getting "SubCats is not defined".

const getSubCategories = asyncHandler(async (req, res) => {
   const subcategories = await Category.find({SubCats})
   res.json(subcategories)
})

Answer 1

find() returns an array and it takes in an object to query the db. In your question you used Category.find({SubCats}) which is Category.find({SubCats: SubCats}) , which SubCats is not defined.

I think what you are looking for is Category.find().select('SubCats') , this will return an array of Categories with SubCats only.