how to sort array inside collection record in mong

Question

MongoDB noob here...

Ok, I have a collection of students, each with a record that looks like the following.... I want to sort the 'type' : 'homework' scores in descending order.

what does that incantation look like on the mongo shell?

> db.students.find({'_id': 1}).pretty()
{
        "_id" : 1,
        "name" : "Aurelia Menendez",
        "scores" : [
                {
                        "type" : "exam",
                        "score" : 60.06045071030959
                },
                {
                        "type" : "quiz",
                        "score" : 52.79790691903873
                },
                {
                        "type" : "homework",
                        "score" : 71.76133439165544
                },
                {
                        "type" : "homework",
                        "score" : 34.85718117893772
                }
        ]
}

I'm trying this incantation....

 doc = db.students.find()

 for (_id,score) in doc.scores:
     print _id,score

but it's not working.

Answer 1

this work for me, it is a little rough code but the results of the lowest tasks for each student are correct.

var scores_homework = []
db.students.find({"scores.type": "homework"}).forEach(
  function(s){
    s.scores.forEach(
        function(ss){
            if(ss.type=="homework"){
                ss.student_id = s._id
                scores_homework.push(ss)
            }
        }
    )
})
for(i = 0; i < scores_homework.length; i++)
{
    var b = i+1;
    var ss1 = scores_homework[i];
    var ss2 = scores_homework[b];
    var lowest_score = {};
    if(ss1.score > ss2.score){
        lowest_score.type = ss2.type;
        lowest_score.score = ss2.score;
        db.students.update({_id: ss2.student_id},{$pull: {scores: {score: lowest_score.score}}});
    }else if(ss1.score < ss2.score){
        lowest_score.type = ss1.type;
        lowest_score.score = ss1.score;
        db.students.update({_id: ss1.student_id},{$pull: {scores: {score: lowest_score.score}}});
    }else{
        lowest_score.type = ss1.type;
        lowest_score.score = ss1.score;
        db.students.update({_id: ss1.student_id},{$pull: {scores: {score: lowest_score.score}}});
    }
    i++
}