Need to do a many comments belong to one article relation MongoDB - node.js

Question

I am using Mongoose/MongoDB and I am trying to associate many comments to one article. My app begins by scraping from a website and then the user has the option to save each article that was scraped into the MongoDB. When the user chooses to save one article, I save it into database. So when a user clicks on one of their saved articles, they can comment on them. Each article has its own comment section I need to retrieve the correct comments.
//My post comment request in JS file
function postComment(){
var articleComment = {
comment: $('#comment').val().trim()
}
$.post('/comments/' + articleID, articleComment).done(function(data){
$('.main-popup').fadeOut();
console.log('DONNE', data);
});
}
//Post route in controller
router.post('/comments/:id', function(req, res){
var newComment = new Comment(req.body);
newComment.save(function(err, doc){
if(err){
console.log(err);
}else{
Comment.findOneAndUpdate({ "_id": doc._id }, { "article": req.params.id }).exec(function(err, doc){
if(err){
console.log(err);
res.send(err);
}else{
res.send(doc);
}
});
}
});
});
//Get request to get correct comments when clicked on specific article
function showCommentBox(){
$('.comments').empty();
$('#comment').val("");
articleID = $(this).attr('data-article-id');
$.get('/comments/' + articleID, function(data){
if(data.article){ //This is undefined*********************
for(var x = 0; x < data.comment.length; x++){
$('.comments').append("<div><h2>" + data.comment[x].comment + "</h2><span><button>×</button></span></div>");
}
}
$('.main-popup').fadeIn();
});
}
//Get route in controller
router.get('/comments/:id', function(req, res){
Comment.findOne({ "article": req.params.id }).populate("article").exec(function(err, doc){
if(err){
console.log(err)
}else{
res.json(doc);
}
});
});
//Article Model
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ArticleSchema = new Schema({
title: {
type: String
},
link: {
type: String
},
description: {
type: String
},
img: {
type: String
}
});
var Article = mongoose.model("Article", ArticleSchema);
module.exports = Article;
//Comment Model
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var CommentSchema = new Schema({
comment: {
type: String
},
article: {
type: Schema.Types.ObjectId,
ref: 'Article'
}
});
var Comment = mongoose.model('Comment', CommentSchema);
module.exports = Comment;

Answer 1

First, you're missing $set when you do .findOneAndUpdate. Also I think you should convert a string to Mongo ObjectId before setting it.
So it might look likt this:
const ObjectId = mongoose.Types.ObjectId;
Comment.findOneAndUpdate({ "_id": doc._id }, {$set: {"article": new ObjectId(req.params.id) }})
Also you don't need to make 2 database calls. You could article id before saving newComment and then simply send it as a response like this:
//Please notice that mongoose.Schema.Types.ObjectId and mongoose.Types.Object are different types.
//You need this one here:
const ObjectId = mongoose.Types.ObjectId;
router.post('/comments/:id', function(req, res){
var newComment = new Comment(req.body);
newComment.article = new ObjectId(req.params.id);
newComment.save(function(err, doc){
if (err) {
console.error(err);
res.send(err);
return;
}
res.send(doc);
});
});