MongoDB shell : print results - mongodb

Question

If I execute ONLY the 1st part of the following short script in Robo3T, I get the results printed to the screen.
If I execute it with 2nd part, I only get the standard answer "Script executed successfully, but there are no results to show".
How can I print intermediate results such as those expected for 2nd part ?
I precise that concession & mission are both similar JSON objects.
I spent hours on this simple question. Please help.
var mission = db.mission.find({"googleCalendarEventId":"QiVJdbL"});
while (mission.hasNext()) {
var record = mission.next();
print(record.googleCalendarEventId + "," + record.concessionIdSet[0])
};
// 2nd part //
var concession = db.cursor.findOne({"_id": ObjectId(mission.concessionIdSet[0])});
while (concession.hasNext()) {
var record = concession.next();
print(record)
};

Answer 1

Thanks again #stennie, for others who would have the same issues, here's one code that worked for me and the 2 errors I committed :
1/ difference between find (--> cursor) and findOne (--> 1 element)
2/ actions in the loop had to be nested inside the loop --> I used a function and it works:
const missions = db.mission.find({
$and:[{"concessionToInvoice": {$exists: false}},
{"concessionIdSet":{$size:1}}]
});
missions.forEach((mission) => {
const concession = getConcession(mission);
print(mission.googleCalendarEventId+"- invoice to :"+concession.name);
mission.concessionToInvoice = getConcessionToInvoice(concession); //another function
db.mission.save(mission);
});
function getConcession(mission){
const concession = db.concession.findOne({"_id": ObjectId(mission.concessionIdSet[0])});
return concession;
}