En supposant que vous puissiez obtenir la date actuelle...
// the start of the day (midnight)
begin_date_range = ISODate("2012-06-12T00:00:00Z");
// the start of the next day (at midnight)
// this can also be done with 11:59:59PM of the current date using $lte
end_date_range = ISODate("2012-06-13T00:00:00Z");
results = db.collection_name.where({"chashi_ts":{
"$gte":begin_date_range,
"$lt":end_date_range}
);