get data into schema by id in mongoose - node.js

Question

i have two schema i would like to get some info from another schema for example (firstName, lastName) from the userSchema by id that i would provide when adding new comment on the CommentsSchema
const CommentsSchema = new mongoose.Schema({
userId: {
type: String,
required: true
},
commentText: {
type: String,
required: true
},
time: {
type: Date,
default: Date.now
}
});
const UserSchema = new mongoose.Schema({
userName: {
type: String,
required: true
},
firstName: {
type: String,
required: true
},
lastName: {
type: String,
required: true
}
});

Answer 1

You can use mongoose populate to get data from a referenced collection.
First you need to change comments schema to set up a reference to the User model.
You may need to change ref value, if you used a different user model name when you applied mongoose.model("User", UserSchema).
const CommentsSchema = new mongoose.Schema({
userId: {
type: mongoose.Schema.Types.ObjectId,
ref: "User",
required: true
},
commentText: {
type: String,
required: true
},
time: {
type: Date,
default: Date.now
}
});
Let's say you have this user in users collection:
{
"_id": "5e312d5cab2e5028b8865be3",
"userName": "Mongoose",
"firstName": "Buk",
"lastName": "Lau",
"__v": 0
}
And this comment from this user:
{
"_id": "5e312d9cab2e5028b8865be4",
"userId": "5e312d5cab2e5028b8865be3",
"commentText": "this is a comment",
"time": "2020-01-29T07:00:44.126Z",
"__v": 0
}
Now you can access the user info from comment like this:
router.get("/comments/:id", async (req, res) => {
const result = await Comment.findById(req.params.id).populate("userId");
res.send(result);
});
The result will be like this:
{
"_id": "5e312d9cab2e5028b8865be4",
"userId": {
"_id": "5e312d5cab2e5028b8865be3",
"userName": "Mongoose",
"firstName": "Buk",
"lastName": "Lau",
"__v": 0
},
"commentText": "this is a comment",
"time": "2020-01-29T07:00:44.126Z",
"__v": 0
}