router.js

router.get("/semester", async (req, res) => {
  var data = req.query;
  console.log(data.str + " " + data.end);
  var str = data.str;
  var end = data.end;
  var query = [
    {
      $match: {
        Year: {
          $gte: "$$str",
          $lt: "$$end"
        }
      }
    },
    {
      $group: {
        _id: {
          Year: "$Year",
          Semester: "$Semester"
        },
        total: {
          $sum: "$Students"
        }
      }
    },
    {
      $sort: {
        _id: -1
      }
    }
  ];

  var cursor = await Record.aggregate(query);
  console.log(cursor);

  res.status(200).send({ message: "success" });
});