Convert Field With Unix TimeStamp to Date (Mongodb/NodeJS) - node.js

Question

I am using aggregate in MongoDB to group fields by $year, $month & $dayOfMonth.
Transaction.aggregate(
[{
$group: {
_id: {
year : { $year : "$createdAt" },
month : { $month : "$createdAt" },
day : { $dayOfMonth : "$createdAt" },
},
totalQuantity: {
$sum: "$totalQuantity"
},
totalAmount: {
$sum: "$totalAmount"
},
totalPayment: {
$sum: "$totalPayment"
},
count: { $sum: 1 }
}
}
]).then( res => console.log(res));
In the above code, I'm using the default $createdAt field but when I try to use $date which has the date in Unix timestamp, it throws an error.
What have I tried?
Transaction.aggregate(
[{
$group: {
_id: {
year : { $year : new Date("$date") },
month : { $month : new Date("$date") },
day : { $dayOfMonth : new Date("$date") },
},
totalQuantity: {
$sum: "$totalQuantity"
},
totalAmount: {
$sum: "$totalAmount"
},
totalPayment: {
$sum: "$totalPayment"
},
count: { $sum: 1 }
}
}
]).then( res => console.log(res));
But this didn't work as "$date" is passed as a string to the Date constructor. Any workaround this?

Answer 1

You can do it with $toDate, converts unix timestamp milisecond to iso date,
$addFields to convert createdAt and replace value
{
$addFields: {
createdAt: { $toDate: "$createdAt" }
}
},
you can use directly in $group
{
$group: {
_id: {
year: { $year: "$createdAt" },
month: { $month: "$createdAt" },
day: { $dayOfMonth: "$createdAt" }
}
}
}
Playground: https://mongoplayground.net/p/-gWq0YLtLSX
you can convert inside $group also, but this will convert three time and instead of this you can add one time and use in group like above example.
year: { $year: { $toDate: "$createdAt" } },
month: { $month: { $toDate: "$createdAt" } },
day: { $dayOfMonth: { $toDate: "$createdAt" } }