How do i use dynamic query in mongoose

I have created an employee attendance application where attendances are logged and stored in a database. I have been able to obtain a count of the particular date-field with the value of “Present”
the code is written like so :

Employee.collection.countDocuments({"attendances.2019-08-26":"Present"},(err,data)=>
{ if(err){    
   res.status(500) 
      res.send(err) 
}else{      
 res.status(200)       
res.json(data) 
}
 })

// mongoDb database records

{
        "_id": "5d6565236574b1162c349d8f",
        "name": "Benjamin Hall",
        "department": "IT",
        "origin": "Texas",
        "employDate": "2019-08-27",
        "__v": 0,
        "attendances": {
            "2019-08-28": "Sick"
        }
    },
    {
        "_id": "5d6367ee5b78d30c74be90e6",
        "name": "Joshua Jaccob",
        "department": "Marketing",
        "origin": "new york",
        "employDate": "2019-08-26",
        "__v": 0,
        "attendances": {
            "2019-08-26": "Present",
            "2019-08-27": "Sick"
        }
    },
              // output is 1

//schema

const Schema = mongoose.Schema;
const employeeSchema = new Schema({
  name: String,
  department: String,
  origin: String,
  employDate: String,
  attendances: Object
});
module.exports= Employee = mongoose.model('Employee', employeeSchema);

How can I create a dynamic query, for instance, how do I get all document with “present” in the last 7 days? really wish someone will help out!