[{allDatesInitialCompletedTimes:[{date:ISODate("2023-07-09T18:00:00.000Z"),localDate:"2023-07-10",completedTime:0},{date:ISODate("2023-07-10T18:00:00.000Z"),localDate:"2023-07-11",completedTime:0},{date:ISODate("2023-07-11T18:00:00.000Z"),localDate:"2023-07-12",completedTime:0},{date:ISODate("2023-07-12T18:00:00.000Z"),localDate:"2023-07-13",completedTime:0},{date:ISODate("2023-07-13T18:00:00.000Z"),localDate:"2023-07-14",completedTime:0},{date:ISODate("2023-07-14T18:00:00.000Z"),localDate:"2023-07-15",completedTime:0},{date:ISODate("2023-07-15T18:00:00.000Z"),localDate:"2023-07-16",completedTime:0}],existingDatesCompletedTimes:[{date:ISODate("2023-07-12T23:26:52.015Z"),localDate:"2023-07-13",completedTime:179140},{date:ISODate("2023-07-12T00:41:58.208Z"),localDate:"2023-07-12",completedTime:393575},{date:ISODate("2023-07-11T05:14:39.234Z"),localDate:"2023-07-11",completedTime:49076},{date:ISODate("2023-07-15T01:16:24.766Z"),localDate:"2023-07-15",completedTime:298040},{date:ISODate("2023-07-14T01:08:24.053Z"),localDate:"2023-07-14",completedTime:1512468}]}]

db.collection.aggregate([{$project:{allDatesInitialCompletedTimes:{$map:{input:"$allDatesInitialCompletedTimes",in:{$cond:[{$in:["$$this.localDate","$existingDatesCompletedTimes.localDate"]},{"$arrayElemAt":["$existingDatesCompletedTimes",{"$indexOfArray":["$existingDatesCompletedTimes.localDate","$$this.localDate",]}]},"$$this"]}}}}}])