Dynamic field names in MongoDB using Mongoose

. Sample of collection Flights :

 {
        "Orig" : "AGP",
        "Dest" : "CMN",
        "Description_Flight" : "One-Stop-Narrow Type",
        "Description_Flight_2" : "WESTERN EUROPE/WESTERN EUROPE",
        "Mkt_Al" : "0B"

  }

. Sample of collection Coeff :

{
    "Regions" : "WESTERN EUROPE/WESTERN EUROPE",
    "Non-Stop-Narrow Type" : 2.4109,
    "Non-Stop-Supersonic" : 2.71828,
    "One-Stop-Narrow Type" : 2.22554,
    "One-Stop-Turbo" : 0.92312,
    "One-Stop-Wide Type" : 11.24586,
    "One-Stop Online-Turbo" : 0.07577

}

What I want ?

I Have my starting collection, Flights and for each document I want to put a score, a score which based on the Description_Flight_2 and Description_Flight.

Example :

For example, in my sample I have :

        "Description_Flight" : "One-Stop-Narrow Type",
        "Description_Flight_2" : "WESTERN EUROPE/WESTERN EUROPE",

So, I should go to the Coeff collection, and find the region :

          "WESTERN EUROPE/WESTERN EUROPE"

and then take the appropriate value, here I should take this value in this line :

        "One-Stop-Narrow Type" : 2.22554,

I have tried this :

    mongoose.connect('mongodb://localhost/mydb');

var cSchema = new Schema({},{ strict: false, collection: 'flights' }),    
    dflights = mongoose.model("flights", cSchema);
var rSchema = new Schema({},{ strict: false, collection: 'coeff' }), 
    coeff = mongoose.model("coeff", rSchema);
    mongoose.set('debug', false);

    mongoose.connection.on("open", function (err) { 
    if (err) throw err;  


    dflights.find({}).lean().exec(function (err, flights) {  
    if (err) throw err; 

    flights.forEach(function(flight) { 

var Flight_Description = "", score =0 ;

    coeff.findOne({Regions : flight.Description_Flight_2}).lean().exec(function (err, coef) {

And here the important lines :

    Flight_Description = flight.Description_Flight;
    score = (coef != null ) ?  coef.Flight_Description : "Missed data";

Here the last lines

if ( score != 0) 
    dflights.collection.update({_id:flight._id}, { $set : { score :score } } );        
});
});
});
});

Please how can I achieve the above ?

The correct code should be:

score = (coef != null ) ?  coef[Flight_Description] : "Missed data";