Mongoose query specific date range and also get null values

Question

I have a situation where i need to get the dates between specific dates and also get the dates which are not thr (meaning which are empty)

Below is the way of query that am presuming to work like, please help me get corrected.

EvaluationTraining.find({
    mnguser: userid,
    evalDate: "", //i want the empty ones too
    evalDate: {
        '$gte': firstDay,
        '$lte': lastDay
    }
    })
    .sort({evalDate: 'desc'})
    .then(function(eval){
      //results
    })
    .catch(function(err){
      //err
    })

Thanks in advance

Answer 1

try this

EvaluationTraining.find({
    mnguser: userid,
    $or: [{
        evalDate: ""
    }, {
       evalDate:{ 
        '$gte': firstDay,
        '$lte': lastDay
       }
    }]
})

Answer 2

In case we need to find fields which is not present in a few documents instead of empty data, we can use $exists

EvaluationTraining.find({
    mnguser: userid,
    $or: [{
        evalDate: { $exists: false }
    }, {
       evalDate:{ 
        '$gte': firstDay,
        '$lte': lastDay
       }
    }]
})