How to select deep nested data in mongodb using mongoose in nodejs

Question

I am new to nodejs and mongoose and i have created a categories document, which have categories and sub categories and sub categories even has sub categories. Now i want to select the values from level 3 and i am unable to get success.

Here is what my categories looks like

[{
"_id": "58eb0ee37c1f817864b5b863",
"name": "Electronics",
"slug": "electronics",
"order": 1,
"__v": 0,
"subCats": [{
    "name": "Mobiles",
    "slug": "mobiles",
    "_id": "58eb0ee37c1f817864b5b867",
    "subCats": [{
        "name": "Apple",
        "slug": "apple",
        "_id": "58eb0ee37c1f817864b5b872",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "HTC",
        "slug": "htc",
        "_id": "58eb0ee37c1f817864b5b871",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "Mi",
        "slug": "mi",
        "_id": "58eb0ee37c1f817864b5b870",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "OPPO",
        "slug": "oppo",
        "_id": "58eb0ee37c1f817864b5b86f",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "Samsung",
        "slug": "samsung",
        "_id": "58eb0ee37c1f817864b5b86e",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "Lenovo",
        "slug": "lenovo",
        "_id": "58eb0ee37c1f817864b5b86d",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "Motorola",
        "slug": "motorola",
        "_id": "58eb0ee37c1f817864b5b86c",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "LG",
        "slug": "lg",
        "_id": "58eb0ee37c1f817864b5b86b",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "Huawei",
        "slug": "huawei",
        "_id": "58eb0ee37c1f817864b5b86a",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "Nokia",
        "slug": "nokia",
        "_id": "58eb0ee37c1f817864b5b869",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }, {
        "name": "Microsoft",
        "slug": "microsoft",
        "_id": "58eb0ee37c1f817864b5b868",
        "params": ["RAM", "Storage", "Primary Camera", "Front Camera", "Battery", "Processor", "Display Size", "Resolution", "Resolution Type", "GPU", "Operating System"]
    }]
}, {
    "name": "Mobile Accessories",
    "slug": "mobile-accessories",
    "_id": "58eb0ee37c1f817864b5b864",
    "subCats": [{
        "name": "Mobile Cases",
        "slug": "mobile-cases",
        "_id": "58eb0ee37c1f817864b5b866",
        "params": ["Model", "type"]
    }, {
        "name": "Headphones & Headsets",
        "slug": "headphones-headsets",
        "_id": "58eb0ee37c1f817864b5b865",
        "params": []
    }]
}]

Here i want to get _id and name of Apple category and below is what i am doing to fetch the data

router.get('/getparms/:cat', function (req, res, next){

categoriesModel.find({
    "slug" : req.params.cat
} ,function(err, categories){
    if (err) throw err;

    res.send(categories);
})});

Answer 1

You can use Aggregation framework. You can get detailed information here and here .

This code will work fine.

 MyModel.aggregate([ { "$match": { "subCats.subCats.slug": req.params.cat } }, { "$unwind": "$subCats" }, { "$unwind": "$subCats.subCats" }, { "$match": { "subCats.subCats.slug": req.params.cat } }, { "$project": { "data":"$subCats.subCats" } } ], function (err, result) { console.log(result); }) 

Here we matched the document first to reduce other unnessary documents by $match and after unwinding subCats twice, we again matched the parameter and at last we returned only the innner subCats document.