MongoDB sum aggregation with conditionals

I am working on an aggregation to perform some analytics on an Orders object, i want to get the total price from every order from the previous month, and the total from this month, I tried passing in the $match parameter, with the appropriate time conditionals but its not aggregating any of the data. even though if i perform a countDocuments query with the same time conditionals i get a number of documents returned.

    const totalThis = await Order.aggregate([
      {
        $match: {
          // should cut the amount of orders off at the beginning of the current month
          createdAt: { $gte: thisMonth.getMonth() + 1 },
        },
      },
      {
        $group: {
          // using $group, _id has to be there or it doesnt
          // return anything, though we dont need an _id
          _id: null,
          total: {
            $sum: "$totalPrice",
          },
        },
      },
    ]);
    res.status(200).json({
      lastMonth: lastMonthSales,
      thisMonth: thisMonthSales,
      totalSalesLast: totalLast,
      totalSalesThis: totalThis,
    });

in my Postman request, lastMonth returns 0, so it would make sense that the array returned to totalSalesLast would be empty, however thisMonth returns 5 documents, so it should work. obviously if i remove the $match conditional it will aggregate all the documents, but thats because its doing ALL the documents and not actually filtering.

>Solution :

To query the document with createdAt in specific month, your $match stage should be as below:

1. $month – Take the month value from createdAt.
2. $eq – Compare both month from (1) and input month are same.

{
  $match: {
    $expr: {
      $eq: [
        {
          "$month": "$createdAt"
        },
        thisMonth.getMonth() + 1
      ]
    }
  }
}

Sample Mongo Playground