mongoose-self-reference.js

/**
 * Method for create recursively (tree) structure in self referenced mongoose
 * Model
 * 
 * @param  {constructor} model A mongoose.model instance for schema
 *                             validation
 * @param  {Object}      obj   The plain object to be inserted
 * @param  {String}      field The field of the obj/Model
 * 
 * @return {model}  An instance of the Model 'model'
 */
function recursive_reference(model, obj, field) {
  if(obj[field] && obj[field].length) {
    var newObjs = []

    obj[field].forEach(function(d) {
      newObjs.push( recursive_reference(model, d, field) );
    });

    obj[field] = newObjs
  }

  return new model(obj)
}

/**
 * Define the mongoose schema and model
 */

var mongoose = require('mongoose');

var FolderSchema = new mongoose.Schema({
  label: {type: String},
  // set the self reference
  folders: [this],
});

var FolderModel = mongoose.model('folders', FolderSchema);

FolderSchema.pre('save', function(next) {
  if (this.isNew) {
    recursive_reference(FolderModel, this, "folders")
  }

  next();
});

module.exports = FolderModel;

// example of data
{
  "_id": "588e34b4c00784891be9354a",
  "label": "Root Folder",
  "folders": [{
    "_id": "57b23504dd49e2265835041e",
    "label": "My Folder 1",
    "folders": []
  },{
    "_id": "57a9eddc5d9221a11a75fd9b",
    "label": "My Folder 2",
    "folders": []
  },{
    "_id": "580937552de886fa6e9e4992",
    "label": "My folder 3",
    "folders": [{
      "_id": "55a43eb8ac57a491230028fb",
      "label": "My Folder 3.1",
      "folders": []
    }]
  }]
}

// example of data without the recursive_reference no _id is created on
// subfolders, because they are interpreted as raw data;
{
  "_id": "588e34b4c00784891be9354a",
  "label": "Root Folder",
  "folders": [{
    "label": "My Folder 1",
    "folders": []
  },{
    "label": "My Folder 2",
    "folders": []
  },{
    "label": "My folder 3",
    "folders": [{
      "label": "My Folder 3.1",
      "folders": []
    }]
  }]
}

how to apply it in Typescript language.
ever tried someting like this line

...

var FolderSchema = new mongoose.Schema({
    label: {type: String},
    // set the self reference
+   folders: [this],
});

...

error will appear

'this' implicitly has type 'any' because it does not have a type annotation.

how to apply it in Typescript language. ever tried someting like this line

...

var FolderSchema = new mongoose.Schema({
    label: {type: String},
    // set the self reference
+   folders: [this],
});

...

error will appear

'this' implicitly has type 'any' because it does not have a type annotation.

const FolderSchema = new mongoose.Schema({
      label: {type: String},
      folders: [this],
});

FolderSchema.add({
      folders: [FolderSchema],
});