Express, Mongodb (mongoose) - Data comparison and count - mongodb

Question

In my mongodb database i have datas like:
{ id: 'ran1', code: 'ABC1', createdAt: 'Sep 1 2022', count: 5 }
{ id: 'ran2', code: 'ABC1', createdAt: 'Sep 2 2022', count: 3 }
{ id: 'ran3', code: 'ABC2', createdAt: 'Sep 1 2022', count: 2 }
{ id: 'ran4', code: 'ABC1', createdAt: 'Oct 1 2022', count: 1 }
{ id: 'ran5', code: 'ABC1', createdAt: 'Oct 2 2022', count: 2 }
{ id: 'ran6', code: 'ABC2', createdAt: 'Ocr 1 2022', count: 1 }
now as an output i want all the data from October but i also want to count and compare the percentage.
So the output for October will be
{code: 'ABC1', totalCount: the sum of total count of oct (1+2) =3 , percent: (total count of oct - total count of sep)/total count of oct * 100 }
{code: 'ABC2', totalCount: 1, percent: -100}
I tried to achieve these output using two different aggregation and later map the current month aggregation with each element from previous month aggregation. But i think there are some better solution.
Here is my code
const { filterDate, shop } = req.query;
const splittedFilter = filterDate.split("-");
const query = {
shopUrl: { $regex: shop, $options: "i" },
createdAt: {
$gte: new Date(splittedFilter[0]),
$lte: new Date(splittedFilter[1]),
},
};
const currentCodes = await BlockedCode.aggregate([
{
$match: query,
},
{
$group: {
_id: "$discountCode",
totalCount: { $sum: "$count" },
},
},
]);
const prevQuery = {
shopUrl: { $regex: shop, $options: "i" },
createdAt: {
$gte: new Date(splittedFilter[2]),
$lte: new Date(splittedFilter[3]),
},
};
const previousCodes = await BlockedCode.aggregate([
{
$match: prevQuery,
},
{
$group: {
_id: "$discountCode",
totalCount: { $sum: "$count" },
},
},
]);
const result = currentCodes.map((code) => {
const foundPrevCode = previousCodes.find((i) => i._id === code._id);
if (foundPrevCode?._id) {
const prevCount = foundPrevCode?.totalCount;
const currCount = code?.totalCount;
const difference = currCount - prevCount;
const percentage = (difference / currCount) * 100;
return { ...code, percentage };
} else {
return { ...code, percentage: 100 };
}
});

Answer 1

#shahamar Rahman i don't understand percentage logic can you explain little more!
upto this i filtered and counted the data based October month,plz check it and let me know if it's helps you
https://mongoplayground.net/p/Fet3UUI9LDC
db.collection.aggregate([
{
$addFields: {
month: {
$month: {
$toDate: "$createdAt"
}
}
}
},
{
$match: {
month: 10
}
},
{
$group: {
_id: {
code: "$code"
},
count: {
$sum: "$count"
}
}
}
])