'How to prevent duplicates in nested array mongoose?

I am trying to prevent duplicates on today's date when the students are taking attendance.

For example, every day students are to take attendance but when a student named John submit multiple times for today's attendance, my MongoDB would have many duplicate entries for John's today's attendance.

Here is my schema:

const attendanceSchema = mongoose.Schema({
    courseTitle: { type: String, trim: true },
    courseStartDate: {type: Date},
    courseEndDate: {type: Date},
    enrollment: [{
        studentID: { type: String, trim: true},
        studentName: { type: String, trim: true },
        attendance: [{
            datenumber:{type:Number},
            attendanceDate: { type: Date},
        }],
    }],
}, { timestamps: true });

Here is my node/express code:

router.post('/attendance/takeattendance', async (req, res) => {

 const todaydatenumber = moment().format("YYYYMMDD")

  const attendanceTaking = {
          datenumber: datenumber,
          attendanceDate: moment().format('YYYY-MM-DD, hh:mm:ss a')
    }

        await Attendance.findOneAndUpdate({ _id: {"$eq": courseid}},
          {
            $push: {
              "enrollment.$[enroll].attendanceTaking":attendanceTaking
            },
          },{arrayFilters:[{ "enroll._id": req.params.studentid }]})
          return res.json({ statusCode: "200", msg: 'Attendance taken for today! Thanks.' });
      } 
}

How should I prevent the duplicate date for today's attendance? Thanks

Update:

When I tried to query for today date 20220330 using this code here:

   let attendanceExist = await Attendance.findOne({ enrollment: { $elemMatch: { studentUUID: { "$eq": student.studentUUID }, "enrollment.attandanceTaking": { $elemMatch: { datenumber: { "$eq": 20220330 } } } } } })

Here is the data I am trying to query:

_id : 6210834ce3a7b51ad5bde65e
courseTitle : "Some Course Title"
courseStartDate:2022-02-20 07:30:00.000
courseEndDate:2022-02-24 07:30:00.000
attendanceStatus:"Open"
enrollment:Array
    0:Object
        studentUUID:"6506de7b0d32492c878307a1992f54e8"
        studentName:"John Doe"
        _id:6242d542af9da06f9e69eb1f
        
        attendanceTaking:Array
            0:Object
                datenumber:20220329
                attendanceDateAM:2022-03-29 12:14:40.000
                attendanceDatePM:1900-01-01 01:04:35.000
                _id:6243d93072c09377877ee501
            1:Object
                datenumber:20220330
                attendanceDateAM:2022-03-30 13:44:26.000
                attendanceDatePM:1900-01-01 01:04:35.000
                _id:6243ee3a7c0a73ed7ed49c54
createdAt:2022-02-19 13:42:36.946
updatedAt:2022-03-30 13:44:43.786
__v:0

But when I console.log(attendanceExist), I am getting null when I should be getting some results

mongoose


Solution 1:[1]

You can add conditions depending on existing data something like this

    let attendanceExist = await Attendance.find({enrollment: {
    $elemMatch: {
      studentId: //id,attandance: {$elemMatch: {dateNumber://date}}
    }}})
    
    if(attendanceExist)
    {
    return
    }
    
    else{
    //your insert query
    }

Suggestion - You can handle it with front end also, if a student marked the attendance for today the button should be disabled or hidden after marking

Sources

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Source: Stack Overflow

Solution Source
Solution 1

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