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db.collection.aggregate([{"$set":{"data":{"$map":{"input":"$data","as":"d","in":{"count":"$$d.count","dataItems":"$$d.dataItems","topDevice":{$function:{body:"function(arr) {return arr.sort((a,b) =>arr.filter(v => v===a).length-arr.filter(v => v===b).length).pop() }",args:["$$d.dataItems.device"],lang:"js"}},"topLocation":{$function:{body:"function(arr) {return arr.sort((a,b) =>arr.filter(v => v===a).length-arr.filter(v => v===b).length).pop() }",args:["$$d.dataItems.city"],lang:"js"}}}}}}}])