Mongoose aggregate, Match, Count, Group - node.js

Question

I am trying to send a list of total paid and unpaid client with count along with data from my node API.
In mongoose method, I am stuck at thinking how to go further.
can anyone suggest the best way to achieve this?
router.get("/", ensureAuthenticated, (req, res) => {
Loan.aggregate([
{
$match: {
ePaidunpaid: "Unpaid"
}
}
]).then(function(data) {
console.log(data);
res.render("dashboard", { admin: req.user.eUserType, user: req.user,data:data });
});
});
Loan Model:
const Loan = new Schema({
sName: { type: String },
sPurpose: [String],
sBankName: String,
sBranchName: [String],
nTotalFees: { type: Number },
ePaidunpaid: { type: String ,default:'Unpaid'},
sCashOrCheque: { type: String },
});
Outcome:
Details of a user with a count of paid and unpaid clients
[
Paid:{
// Paid users
},
Unpaid:{
// Unpaid Users
},
]

Answer 1

Well in that case, try this -
Loan.aggregate([
{
$group: {
_id: "$ePaidunpaid",
data: { $push: "$$ROOT" },
count: { $sum: 1 }
}
}
]);
Output would be something like this -
{
"_id": "Paid",
"data": [
// All the documents having ePaidunpaid = Paid
{ _id: "asdasd123 1eqdsada", sName: "Some name", // Rest of the fields },
{ _id: "asdasd123 1eqdsada", sName: "Some name", // Rest of the fields }
],
count: 2
},
{
"_id": "Unpaid",
"data": [
// All the documents of having ePaidunpaid = Unpaid
{ _id: "asdasd123 1eqdsada", sName: "Some name", // Rest of the fields },
{ _id: "asdasd123 1eqdsada", sName: "Some name", // Rest of the fields }
],
count: 2
},
Explanation
First stage of the pipeline $group groups all the documents according to ePaidunpaidfield which only have two values Paid or Unpaid thus rendering only two documents respectively.
Next step is to accumulate original data (documents) being grouped together. This is achieved using $push accumulator on data field, pushing $$ROOT which effectively references the document currently being processed by pipeline stage.
Since you needed count of all paid and unpaid users hence a $sum accumulator to count all the items in each group.