I want to pass array object inside array subdocument in mongoose - node.js

Question

Here is my Schema
I am trying to add replies array inside answers array. If someone answers a question and if someone wants to reply on the given answer
const mongoose = require("mongoose");
const { ObjectId } = mongoose.Schema;
const questionSchema = new mongoose.Schema(
{
postedBy: {
type: ObjectId,
required: true,
ref: "User",
},
question: {
type: String,
required: true,
},
photo: {
data: String,
required: false,
},
answers: [
{
userId: { type: ObjectId, ref: "User" },
answerType: {
data: String,
required: false,
},
answer: String,
replies: [
{
userId: { type: ObjectId, ref: "User" },
reply: String,
replyType: {
data: String,
required: false,
},
},
],
},
],
questionType: {
data: String,
required: false,
},
createdAt: {
type: Date,
required: true,
default: Date.now,
},
},
{ timeStamps: true }
);
module.exports = mongoose.model("Question", questionSchema);
Here is my Controller method
exports.postReply = (req, res) => {
const reply = req.body.reply || "";
const userId = req.user._id || "";
const answerId = req.body.answerId || "";
Question.findByIdAndUpdate(
{ _id: answerId },
({ $push: { answers: { answer: { replies: { reply, userId } } } } },
{ new: true }),
(err, newReply) => {
if (err) {
res.status(400).json({
error: errorHandler(err),
});
} else {
res.json({
msg: "Reply posted successfully",
newReply,
});
}
}
);
};
I feel I am going wrong on the findOneAndUpdate method. I am getting no error on the console but newReply comes null. Any help will be appreciated.

Answer 1

I would suggest you using the $addToSet instead of the $push operator as you are adding a document to the array. (see: https://docs.mongodb.com/manual/reference/operator/update/addToSet/).
If you want to add more than one document to the array, refer also to the $each operator together with $addToSet.
So your coding can look similiar to this (note: the variable 'yourDocument' is the document you want to add):
Question.findByIdAndUpdate(
{ _id: answerId },
{ $addToSet: { answers: yourDocument } },
{ new: true },
(err, newReply) => {
if (err) {
res.status(400).json({
error: errorHandler(err),
});
} else {
res.json({
msg: "Reply posted successfully",
newReply,
});
}
}
);
};

Answer 2

The problem is clearly the parentesis around
({ $push: { answers: { answer: { replies: { reply, userId } } } } }, { new: true })
Doing this console.log( ({a:1}, {b:2}) ); will log {b: 2} which means you are doing this
Question.findByIdAndUpdate( { _id: answerId }, { new: true }, (err, newReply) => {
So remove the parentesis and you should be good
Question.findByIdAndUpdate(
{ _id: answerId },
{ $push: { answers: { answer: { replies: { reply, userId } } } } },
{ new: true },
(err, newReply) => {
if (err) {
res.status(400).json({
error: errorHandler(err),
});
} else {
res.json({
msg: "Reply posted successfully",
newReply,
});
}
}
);