But now I don't know how to filter
I'm aggregating the filtered data：

[
       {
            "_id": "61cea071cfa3c96b9a4d2657",
            "name": "Utils",
            "children": [
                {
                    "name": "Code",
                    "_id": "61cebb4e6c4a5c643494d1a1",
                    "children": [{name:"jahn"}]
                },
                {
                    "name": "Image",
                    "_id": "61ceb8ad6c4a5c643494d11e",
                    "children": []
                }
            ]
        },
        {
            "_id": "61cea071cfa3c96b9a4d2111",
            "name": "Names",
            "children": [
               {
                    "name": "que",
                    "_id": "61cebb4e6c4a5c643494d1a1",
                    "children": [
                       
                     ]
                },
                {
                    "name": "filter",
                    "_id": "61cebb4e6c4a5c643494d1a1",
                    "children": [
                        {name:"jahn"}
                     ]
                }
            ]
        },
]

Looking forward to your help How to filter out children when children are empty and not displayed
Desired result :

[
        {
            "_id": "61cea071cfa3c96b9a4d2657",
            "name": "Utils",
            "children": [
                {
                    "name": "Code",
                    "_id": "61cebb4e6c4a5c643494d1a1",
                    "children": [
                        {name:"jahn"}
                     ]
                }
            ]
        },
        {
            "children": [
                {
                    "children": [
                        {name:"jahn"}
                     ]
                }
            ]
        },
]

I want if children in children, if it's empty it doesn't show the whole object

CodePudding user response：

If you tried to filter for the second level children array, you can use $filter.

db.collection.aggregate([
  {
    $project: {
      _id: 1,
      name: 1,
      children: {
        "$filter": {
          "input": "$children",
          "cond": {
            "$ne": [
              "$$this.children",
              []
            ]
          }
        }
      }
    }
  }
])

Sample Mongo Playground

Note:

"$ne": [
  "$$this.children",
  []
]

Can be replaced with:

"$ne": [
  {
    $size: "$$this.children"
  },
  0
]