[{a:[3,5,8,1],b:[5,2,6,5],c:[2,6,3,1]}]

db.collection.aggregate([{$set:{"a":{$function:{body:"function(a){a.sort((x, y)=>x-y);return a;}",args:["$a"],lang:"js"}},"b":{$function:{body:"function(b){b.sort((x, y)=>x-y);return b;}",args:["$b"],lang:"js"}},"c":{$function:{body:"function(c){c.sort((x, y)=>x-y);return c;}",args:["$c"],lang:"js"}}}}])