怎么办聚集和组MongoDB中的一个子领域是一个数组？

我建立一个API，用于签入和签员工出去考勤系统。公司为每位员工我需要总结一年的工作一个月，然后总小时数。我试着用聚集，项目组，但我没有收到在一个月或一年的总工时员工。

我的方案的一部分是这样的：

const EmployeeSchema = new Schema({
_id: Schema.Types.ObjectId,
attendance: [{
    date: {type: Date, default: Date.now},
    entry: {type: Date, required: false},
    exit: { 
        time: {type: Date, required: false}
     },
    totalHours: {type: Number, required: false}
}]

)}

对于聚集，我试图实现这种方式：

exports.aggregation = (req, res) => {
const id = req.params.salespersonId;
DailySalesPerson.aggregate([
      {$unwind: "$attendance"}, 
      {
          $group: {
              _id: {
                  month: {"$month":"$attendance.date"}
              },
              totalHours: {$sum: "totalHours"},
              count: {$sum: 1}
          }
      },


])
.then(result => {
    res.status(200).json({result});
})

};

我没有计入每月或每年的员工总小时。

现在我的结果是这样的：

{
    "result": [
    {
        "_id": "5c5bb13c1d92482b148ed17b",
        "attendance": [
            {
                "date": "2019-02-07T04:30:07.391Z",
                "totalHours": 1,
                "month": 2,
                "year": 2019
            },
            {
                "date": "2019-02-07T04:51:05.359Z",
                "totalHours": 1,
                "month": 2,
                "year": 2019
            },
            {
                "date": "2019-02-07T04:56:21.951Z",
                "totalHours": 1,
                "month": 2,
                "year": 2019
            }
        ]
    },
    {
        "_id": "5c5fdb1781165a1e58115da7",
        "attendance": []
    },
    {
        "_id": "5c5fdd1738ec411b1849ce58",
        "attendance": [
            {
                "date": "2019-02-10T08:14:01.201Z",
                "totalHours": 1,
                "month": 2,
                "year": 2019
            }
        ]
    },
    {
        "_id": "5c5fdf6336e9ea24e0e69795",
        "attendance": [
            {
                "date": "2019-02-10T08:23:14.180Z",
                "totalHours": 1,
                "month": 2,
                "year": 2019
            }
        ]
    }
]

}

我需要聚合每个人的每月和每年的工作总小时数。现在我的结果看起来像如上。如何我总和小时的每一天？

您可以使用下面聚集

db.collection.aggregate([
  { "$project": {
    "totalHoursInThisMonth": {
      { "$let": {
        "vars": { "date": {
          "$filter": {
            "input": "$attendance",
            "as": "attend",
            "cond": {
              "$and": [
                { "$gte": ["$$attend.date", startOfMonth] },
                { "$lte": ["$$attend.date", endOfMonth] }
              ]
            }
          }
        }},
        "in": "$$date.totalHours"
      }}
    }
  }}
])