Need to apply two group in sequence and second group should will have effect on result of first group - node.js

Question

I want to group my data on the base of factoryId field and then each factory there will be multiple orders want to again group on basis of orderId as each order can contain multiple items. Here I am giving the example of my data and what I need and first group by which I tried.
{
"_id" : ObjectId("5b3e270c42d8004cea382e87"),
"factoryId" : ObjectId("5aa76190cef23a1561b8056c"),
"productId" : ObjectId("5aa78c66cef23a1561b80893"),
"orderId" : ObjectId("5b3e270c42d8004cea382e86"),
"generatedOrderId" : "3985-166770-4554",
"productName" : "Lakme Lotion"
},
{
"_id" : ObjectId("5b3e270c42d8004cea382e88"),
"factoryId" : ObjectId("5b39aed32832f72062e51c23"),
"productId" : ObjectId("5b3cb96139cec8341df52c4b"),
"orderId" : ObjectId("5b3e270c42d8004cea382e86"),
"generatedOrderId" : "3985-166770-4554",
"productName" : "Coke"
},
{
"_id" : ObjectId("5b3e27b07fe0d94d62b76b2a"),
"factoryId" : ObjectId("5aa76190cef23a1561b8057c"),
"productId" : ObjectId("5ac21075ac347a5fbf355028"),
"orderId" : ObjectId("5b3e27b07fe0d94d62b76b27"),
"generatedOrderId" : "3985-755507-7484",
"productName" : "Spoon"
}
And I want result as:
{
"factoryId":ObjectId("5aa76190cef23a1561b8057c"),
"orders":[
{
"orderId":ObjectId("5b3e270c42d8004cea382e86")
"items":[
{
"productName":"Lakme Lotion"
},
{
"productName":"Coke"
}
]
}
]
}
Can anyone help me with this?. Any help is appreciated.

Answer 1

I tried and It worked for me. Sorry
db.getCollection("transactions").aggregate(
[
{
"$group" : {
"_id" : "$orderId",
"items" : {
"$push" : "$$ROOT"
}
}
},
{
"$project" : {
"orderId" : "$_id",
"items" : "$items",
"_id" : 0
}
},
{
"$unwind" : {
"path" : "$items",
"preserveNullAndEmptyArrays" : false
}
},
{
"$group" : {
"_id" : "$items.factoryId",
"orders" : {
"$push" : "$$ROOT"
}
}
},
{
"$project" : {
"factoryId" : "$_id",
"orders" : "$orders",
"_id" : 0
}
}
]
);