Room.find({}).sort('-date').exec(function(err, docs) { ... });
Room.find({}).sort({date: -1}).exec(function(err, docs) { ... });
Room.find({}).sort({date: 'desc'}).exec(function(err, docs) { ... });
Room.find({}).sort({date: 'descending'}).exec(function(err, docs) { ... });
Room.find({}).sort([['date', -1]]).exec(function(err, docs) { ... });
Room.find({}, null, {sort: '-date'}, function(err, docs) { ... });
Room.find({}, null, {sort: {date: -1}}, function(err, docs) { ... });

如果用后面的几种方法，第二个参数，如果没有必须填写null，否则报错，

更多：https://stackoverflow.com/questions/5825520/in-mongoose-how-do-i-sort-by-date-node-js