Pushing entry into multilevel nested array in MongoDB via mongoose

Question

I am using mongoose in nodejs(express) in backend. My array structure has THREE levels. At third level, some files are present. But I need to add entries at any level as per user demand.

   [
   {
   "name": "A folder at",
    "route": "level1_a"
  },
  {
    "name":"Another folder at Level1",
    "route": "level1_b",
    "children":
        [
            {
            "name": "A folder at Level2",
            "route": "level1_b/level2_a",
            "children": 
                [
                    {
                    "name": "A folder at Level3",
                    "route": "level1_b/level2_a/level3_a",
                    "children":
                        [
                            {
                            "name": "A file at last level",
                            "route": "level1_b/level2_a/level3_a/file1"
                            },
                            {
                            "name": "Add a new File",
                            "route":"level1_b/level2_a/level3_a/new_file"
                            }
                        ]
                    },
                    {
                    "name": "Add Folder at Level3",
                    "route":"level1_b/level2_a/new_folder"
                    }
                ]
            },
            {
                "name": "Add Folder at level2",
                "route":"level1_b/new_folder"
            }
        ]
  },
  {
      "name": "Add Folder at Level1",
      "route":"new_folder"
  }
]

Now I have to add an entry at a specified position. Suppose at level2, I need to add a folder. For adding, two parameters are sent from angular to the backend. These will be 'name' and a 'route'. So my entry would be having {name: 'Products', route: 'level1_a/products'} and similarily should be placed at correct position i.e. inside the children of level1_a. My backend has a schema which would be like:

const navSchema = mongoose.Schema({
name:{type:String,required:true},
route:{type:String},
children:{
    type: {
    name:{type:String,required:true},
    route:{type:String},
 }}
});
module.exports = mongoose.model('NatItems',navSchema);

And the API would be like:

router.post('/navlist',(req,res,next)=>{
  const name= req.body.folder;
  const route= req.body.url;
  console.log(folder,url);//it will be required parameters like name: 'Products', route:'level1_a/products'
  //let pathArray = route.split('/'); //if you want you can split the urls in the array

  //Help me write the code here

  res.status(201).json({
    message:"Post added successfully!"
  })
})

Please help me in adding entries in db. I know navlist.save() adds an entry directly but I am not able to add entries in a nested manner.

PS: I can't change the array structure because this array is easily read by angular and a complete navigation menu is made!! I am working for first time in nodejs and mongoose, so I am having difficulty in writing code with mongoose function.

mickl · Accepted Answer · 2020-09-15 21:06:24Z

4

+50

For the scenario you've provided ({name: 'Products', route: 'level1_a/products'}) the update statement is pretty straightforward and looks like this:

Model.update(
   { route: "level1_a" }, 
   { $push: { children: {name: 'Products', route: 'level1_a/products'} } })

Things are getting a little bit more complicated when there are more than two segments in the incoming route, e.g.

{  "name": "Add a new File", "route":"level1_b/level2_a/level3_a/new_file2" };

In such case you need to take advantage of the positional filtered operator and build arrayFilters and your query becomes this:

Model.update(
    {  "route": "level1_b"},
    {
        "$push": {
                "children.$[child0].children.$[child1].children": {
                    "name": "Add a new File",
                    "route": "level1_b/level2_a/level3_a/new_file2"
                }
            }
        },
    {
        "arrayFilters": [
            {
                "child0.route": "level1_b/level2_a"
            },
            {
                "child1.route": "level1_b/level2_a/level3_a"
            }
        ]
    })

So you need a function which loops through the route and builds corresponding update statement along with options:

let obj = {  "name": "Add a new File", "route":"level1_b/level2_a/level3_a/new_file2" };

let segments = obj.route.split('/');;
let query = { route: segments[0] };
let update, options = {};
if(segments.length === 2){
    update = { $push: { children: obj } }
} else {
    let updatePath = "children";
    options.arrayFilters = [];
    for(let i = 0; i < segments.length -2; i++){
        updatePath += `.$[child${i}].children`;
        options.arrayFilters.push({ [`child${i}.route`]: segments.slice(0, i + 2).join('/') });
    }
    
    update = { $push: { [updatePath]: obj } };
    
}

console.log('query', query);
console.log('update', update);
console.log('options', options);

So you can run:

Model.update(query, update, options);

answered Sep 15, 2020 at 21:06

mickl

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2 Comments

Swapnil Sourabh Over a year ago

Thanks @mickl for an apt answer. The concept of building arrayFilters was completely unknown to me. Happy to award you the bounty xD ! Just one thing, in a case where if(segments.length === 1) i.e. one could also put an entry directly into the array, I used the following in the if block -> {obj.save(); return;} . Can you suggest a better alternative here where I can still use the Update fn?

mickl Over a year ago

@SwapnilSourabh yeah, you need to handle such case as well and just save should be fine, good idea!

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