在流星中插入嵌套对象

我将此文档保存在名为exam 的mongo集合中

// meteor:PRIMARY> db.exam.find()
{
    "_id" : "RLvWTcsrbRXJeTqdB",
    "examschoolid" : "5FF2JRddZdtTHuwkx",
    "examsubjects" : [
        {
            "subject" : "Z4eLrwGwqG4pw4HKX"
        },
        {
            "subject" : "fFcWby8ArpboizcT9"
        }
    ],
    "examay" : "NrsP4srFGfkc5cJkz",
    "examterm" : "5A5dNTgAkdRr5j53j",
    "examclass" : "gYF2wE4wBCRy9a3ZC",
    "examname" : "First",
    "examdate" : ISODate("2016-05-07T22:41:00Z"),
    "examresultsstatus" : "notreleased"
}

我正在尝试从该文档中选择数据，并使用此代码将其保存到另一个文档中。目的是使上面文档中的examsubjects值成为我插入的文档中的密钥。

'click .reactive-table tr': function() {
    Session.set('selectedPersonId', this._id);
    var cursor = Exam.find({ _id:
            Session.get("selectedPersonId")}).fetch();
    cursor.forEach(function(doc){
        for (i = 0; i < doc.examsubjects.length; i++) {
            for (var prop in doc.examsubjects[i]) {
                console.log("obj." + prop + " = " + doc.examsubjects[i][prop]);
                var subj = doc.examsubjects[i][prop];
                Told.insert({
                    examschoolid:"sms",
                    examname:doc.examname,
                    examsubjects: [{subj : "0"}],
                    examay:doc.examay,
                    examterm:doc.examterm,
                    examclass:doc.examclass,
                    examdate:doc.examdate
                });
            }
        }
    });
},

当代码运行时，保持主题值的变量subj只是插入subj，而不知道它是像这样的变量

{
    "_id" : "5yjwFanBAupgu9GHq",
    "examschoolid" : "sms",
    "examname" : "First",
    "examsubjects" : [
        {
            "subj" : "0"
        }
    ],
    "examay" : "NrsP4srFGfkc5cJkz",
    "examterm" : "5A5dNTgAkdRr5j53j",
    "examclass" : "gYF2wE4wBCRy9a3ZC",
    "examdate" : ISODate("2016-05-07T22:41:00Z")
}

为什么变量不被视为变量？。

编辑

'click .reactive-table tr': function() {
    Session.set('selectedPersonId', this._id);
    var cursor = Exam.find({ _id: Session.get("selectedPersonId")}).fetch();
    cursor.forEach(function(doc){
        var sq = function(){
            for (i = 0; i < doc.examsubjects.length; i++) {
                for (var prop in doc.examsubjects[i]) {
                    const subj = doc.examsubjects[i][prop];
                    let subject = {};
                    subject[subj] = "0";
                    return [subject];
                }
            }
        }
        console.log(sq());
        Told.insert({
            examschoolid:"sms",
            examname:doc.examname,
            examsubjects: sq(),
            examay:doc.examay,
            examterm:doc.examterm,
            examclass:doc.examclass,
            examdate:doc.examdate
        });
    });
    //Uncaught TypeError: cursor.count is not a function
},

更新后的代码几乎可以工作，但只插入1条记录。