Querying MongoDB for an Object nested in an Array - node.js

Question

I have a User schema that looks like this:
{
"_id" : ObjectId("5f0cbcdf8363cd155c2570f5"),
"clients" : [
{
"clientName" : "Chabad of Closter",
"activeInvoice" : [
{
"clientName" : "Chabad of Closter",
"startTime" : "2020-07-16T03:06:19.102Z",
"endTime" : "2020-07-16T06:06:19.102Z",
"duration" : "3.00",
"rate" : "25",
"description" : "email",
"total" : "$75.00"
},
{
"clientName" : "Chabad of Closter",
"startTime" : "2020-07-20T18:49:45.300Z",
"endTime" : "2020-07-20T20:49:45.300Z",
"duration" : "2.00",
"rate" : "25",
"description" : "janitor",
"total" : "$50.00"
},
{
"clientName" : "Chabad of Closter",
"startTime" : "2020-07-20T08:02:04.795Z",
"endTime" : "2020-07-20T21:02:04.795Z",
"duration" : "13.00",
"rate" : "35",
"description" : "something",
"total" : "$455.00"
}
],
"pastInvoices" : []
},
{
"clientName" : "Chabad UC",
"activeInvoice" : [
{
"clientName" : "Chabad UC",
"startTime" : "2020-07-14T00:43:30.689Z",
"endTime" : "2020-07-14T03:43:30.689Z",
"duration" : "3.00",
"rate" : "25",
"description" : "website",
"total" : "$75.00"
},
{
"clientName" : "Chabad UC",
"startTime" : "2020-07-14T00:43:30.689Z",
"endTime" : "2020-07-14T03:43:30.689Z",
"duration" : "3.00",
"rate" : "25",
"description" : "website",
"total" : "$75.00"
},
{
"clientName" : "Chabad UC",
"startTime" : "2020-07-16T08:32:44.980Z",
"endTime" : "2020-07-16T08:32:44.980Z",
"duration" : "0.00",
"rate" : "25",
"description" : "something",
"total" : "$0.00"
},
{
"clientName" : "Chabad UC",
"startTime" : "2020-07-20T20:22:27.399Z",
"endTime" : "2020-07-20T20:22:27.399Z",
"duration" : "0.00",
"rate" : 0,
"description" : "",
"total" : "$0.00"
}
],
"pastInvoices" : []
},
{
"clientName" : "Chabad Mobile",
"activeInvoice" : [
{
"clientName" : "Chabad Mobile",
"startTime" : "2020-07-14T04:05:18.084Z",
"endTime" : "2020-07-14T06:05:18.084Z",
"duration" : "2.00",
"rate" : "25",
"description" : "Fema grant",
"total" : "$50.00"
},
{
"clientName" : "Chabad UC",
"startTime" : "2020-07-16T04:56:51.451Z",
"endTime" : "2020-07-16T05:56:51.451Z",
"duration" : "1.00",
"rate" : "25",
"description" : "grants",
"total" : "$25.00"
},
{
"clientName" : "Chabad of Closter",
"startTime" : "2020-07-16T03:56:51.451Z",
"endTime" : "2020-07-16T05:56:51.451Z",
"duration" : "2.00",
"rate" : "26",
"description" : "grants",
"total" : "$52.00"
},
{
"clientName" : "Chabad Mobile",
"startTime" : "2020-07-15T18:51:00.000Z",
"endTime" : "2020-07-16T08:09:20.001Z",
"duration" : "13.31",
"rate" : "22",
"description" : "website",
"total" : "$292.82"
}
],
"pastInvoices" : []
}
],
"username" : "test50#test.com",
"password" : "************************************",
"firstName" : "John",
"__v" : 0
}
I'm trying to query the "clients" array with a value from the "clientName" property.
app.get("/closeinvoice", function(req, res){
// gets the id for the document
const id = req.user._id;
// gets the value of "clientName" for the query
const c = req.query.client;
User.find({_id: id, "clients.clientName": c}, function(err, foundDoc) {
if (err) {
console.log(err)
} else {
console.log(foundDoc);
}
})
})
Each time I do this, MongoDB returns the entire document. I need it to return only one object from the nested array. I'm also wondering if I could be using a different method from the Mongoose API. I would prefer to use "findByID" but I'm not sure if you can for this type of query.

Answer 1

You can take advantage of the $ (projection) operator which returns the first matching element from an array (based on corresponding `$elemMatch):
User.find({ _id: id, clients: { $elemMatch: { clientName: c }}}, { "clients.$": 1}, function(err, foundDoc) { ... })
Mongo Playground