Node js mongoose filter data from array in collection-CodePudding

I am having a response like this ....................................................................................................................................................................................................

{
    "data": [
        {
            "user": "83k13bde05f40640j12075w",
            "products": [
                {
                    "type": "shoes",
                    "amount": 20
                },
                {
                    "type": "trousers",
                    "amount": 6
                }
            ],
            "inStock": false
        },
        {
            "user": "9dc3f7de05f40640j12075y",
            "products": [
                {
                    "type": "chairs",
                    "amount": 11
                },
                {
                    "type": "bags",
                    "amount": 16
                }
            ],
            "inStock": false
        },
        {
            "user": "6wb3f7ne35f40640m62p2gd",
            "products": [
                {
                    "type": "phones",
                    "amount": 2
                },
                {
                    "type": "clothes",
                    "amount": 15
                }
            ],
            "inStock": false
        }
    ]
}

This the function outputting the above response

exports.getProducts = async (req,res) => {
    const result = await Products
     .find({inStock: false})
     .select("-_id -createdAt -__v")
    .exec()
    if(!result) return res.status(400).json({ data: 'No product found' });
    if(result.err) return res.json({ err: err });
      
    return res.json({data: result});
}

But I want to get only products with the amount greater than 10

So my output should be like this

{
    "data": [
        {
            "user": "83k13bde05f40640j12075w",
            "products": [
                {
                    "type": "shoes",
                    "amount": 20
                }
            ],
            "inStock": false
        },
        {
            "user": "9dc3f7de05f40640j12075y",
            "products": [
                {
                    "type": "chairs",
                    "amount": 11
                },
                {
                    "type": "bags",
                    "amount": 16
                }
            ],
            "inStock": false
        },
        {
            "user": "6wb3f7ne35f40640m62p2gd",
            "products": [
                {
                    "type": "clothes",
                    "amount": 15
                }
            ],
            "inStock": false
        }
    ]
}

I tried using

.find({'products.amount': { $gt: 10 }})

But It didn't filter out the response

CodePudding user response：

Did you try the $elemMatch operator ?

const result = await Products
  .find({ 
    inStock: false, 
    products: { $elemMatch: { amount: { $gt: 10 } } } 
  })
  .select("-_id -createdAt -__v")
  .exec();

CodePudding user response：

You can use aggregation to achieve this. First of all you use $match operator to find the documents with items in the array that match with your criteria. Then you can use $project and $filter operator to return the array filtered.

const result = await Products.aggregate([
{
   "$match" : {
       "products" : {
          "$elemMatch" : { amount: { $gt: 10 } }
       },
   }
},
{
   $project: {
      user: 1,
      inStock: 1,
      products: {
        $filter: {
          input: "$products",
          as: "products",
          cond: { $gt: ["$products.amount", 10] }
        }
      }
   }
}
])
.select("-_id -createdAt -__v")
.exec();

For further reading: https://studio3t.com/knowledge-base/articles/filter-elements-from-mongodb-arrays/#how-to-use-filter-and-project