how to control the find() to get all children with parent comment - mongodb

Question

I am a bigenner in mongoose, I implement a concept of comment. In fact, I create a schema comment in which I identify the different fields, as it is shown:
import mongoose from 'mongoose';
/* eslint-disable-next-line */
import db from './db';
// Define Schema method= mongoose;
const { Schema } = mongoose;
const CommentSchema = new Schema({
id: {
type: String,
required: true,
unique: true,
},
author_id: {
type: String,
required: true,
},
content: {
type: String,
},
creation_date: {
type: Date,
default: Date.now,
},
interesting_comment: [String],
updated_content_list: [{ previous_date: Date, previous_content: String }],
children: [String],
});
export default mongoose.model('Comment', CommentSchema);
Note: children is about the response to a parent comment, here is the example:
{
"_id" : ObjectId("60217951f57f24079f885d66"),
"interesting_comment" : [
"6ff10e9"
],
"children" : [
"c13e5487-07ba-4bc9-996e-ef1c8f826b32"
],
"updated_content_list" : [ ],
"id" : "6f169ee4-d22d-49a2-9f71-5dacadecf6bb",
"author_id" : "b08a3310-b3f4-4521-9b1a-2d5667a3ea1d",
"content" : "Hello wijdene",
"creation_date" : ISODate("2021-02-08T17:48:01.026Z"),
"__v" : 4
}
{
"_id" : ObjectId("602179d1f57f24079f885d68"),
"interesting_comment" : [ ],
"children" : [ ],
"updated_content_list" : [ ],
"id" : "c13e5487-07ba-4bc9-996e-ef1c8f826b32",
"author_id" : "111",
"content" : "hi nesrine",
"creation_date" : ISODate("2021-02-08T17:50:09.075Z"),
"__v" : 0
}
I implement this function:
async function ListComment() {
const comments = await Comment.find();
return comments;
}
I want to get all the children by their parent comment, I spend hours and I don't get the idea any help please

Answer 1

I try to fix this problem with lookup:
async function ListComment() {
const comments = await Comment.aggregate([{$unwind:{path:"$children",preserveNullAndEmptyArrays: true}},{$lookup:{from:"comments",localField:"children",foreignField:"id",as:"children"}}]);
return comments;
}
But even the child, it is shown in this way. In fact, I add preserveNullAndEmptyArrays: true to preserve parent which doesn't contain a child. But what I get is the new combination + parent without children+children. I want to remove children, any idea