[{value:"3.14"},{value:"1.77"},{value:"367.223579"}]

db.collection.aggregate([{$addFields:{split:{$split:["$value","."]}}},{$addFields:{whole:{"$arrayElemAt":["$split",0]},fraction:{"$arrayElemAt":["$split",1]},}},{$addFields:{whole:{$reduce:{input:{$range:[0,{$strLenCP:"$whole"}]},initialValue:0,in:{$add:[{$multiply:["$$value",10]},{"$indexOfArray":[["0","1","2","3","4","5","6","7","8","9"],{$substr:["$whole","$$this",1]}]}]}}},fractionVal:{$reduce:{input:{$range:[0,{$strLenCP:"$fraction"}]},initialValue:0,in:{$add:[{$multiply:["$$value",10]},{"$indexOfArray":[["0","1","2","3","4","5","6","7","8","9"],{$substr:["$fraction","$$this",1]}]}]}}}}},{$addFields:{double:{$add:["$whole",{$divide:["$fractionVal",{"$pow":[10,{$strLenCP:"$fraction"}]}]}]}}},{$project:{fraction:0,fractionVal:0,whole:0,split:0}}])