find mongoose matching items inside an array of objects - node.js

Question

I have a mongoose schema with an array of objects...
Im trying to get only matching userID in the array, however the array return all the users if there is even one match.
I have the following on node js
app.get("/myanswers/:id", async (req, res) => {
try {
const q = await posts.find(
{ "postAnswer.userID": req.params.id },
"postAnswer.answer postAnswer._id postAnswer.user postAnswer.userID"
);
res.json(q);
} catch (error) {
res.send(error);
}
});
and i get this result:
[
{
"_id": "6074f2648e9f41497438b37a",
"postAnswer": [
{
"_id": "6074f3858e9f41497438b37b",
"userID": "60579272980cb93ea8a91140",
"user": "admin",
"answer": "Kakashi 🐱‍👤"
}
]
},
{
"_id": "6074f4768e9f41497438b37c",
"postAnswer": [
{
"_id": "6074f5338e9f41497438b37e",
"userID": "6074f4f98e9f41497438b37d",
"user": "barrym",
"answer": "here's the correct sequence. table, add row table headers close row. add row add table data close row close table."
},
{
"_id": "6074f5808e9f41497438b37f",
"userID": "60579272980cb93ea8a91140",
"user": "admin",
"answer": "with TH and TD!"
}
]
}
]
i only want exact match so user barrym shouldn't appear

Answer 1

Demo - https://mongoplayground.net/p/3BV58F3GiS4
Use $ (projection)
Note:- limits the contents of an to return the first element
The positional $ operator limits the contents of an to return the first element that matches the query condition on the array.
db.collection.find(
{ "postAnswer.userID": "6074f4f98e9f41497438b37d"},
{ "postAnswer.$": 1}
)