how to write a mongodb aggregation query for following description - node.js

Question

I need a query for:
whose userids are : "userId" : "111b/c", "userId" : "111a". based on the user ids how many are $eq:light_pad:20 with them i need userId:111b/c-max date,userId:111a-max date
DB data
{ "_id" : ObjectId("5a7c1d167826eaca4b4e4398"), "firstName" : "varun", "secName" : "raju", "userId" : "111a", "light_pad" : "20", "lights" : "on", "CREATE_DATE" : ISODate("2018-05-08T03:12:00Z"), "Department" : "Computer Science and Engg", "Percentage" : "76%", "Address" : { "Street" : "Burkit Road", "City" : "chennai", "State" : "Tamil Nadu" }, "Gender" : "Male" }
{ "_id" : ObjectId("5a7c1db77826eaca4b4e4399"), "firstName" : "raju", "secName" : "rani", "userId" : "111a", "light_pad" : "40", "lights" : "off", "CREATE_DATE" : ISODate("2017-04-08T03:12:00Z"), "Department" : "Computer Science and Engg", "Percentage" : "86%", "Address" : { "Street" : "Burkit Road", "City" : "chennai", "State" : "Tamil Nadu" }, "Gender" : "female" }
{ "_id" : ObjectId("5a7c1e707826eaca4b4e439b"), "firstName" : "ranga", "secName" : "mahesh", "userId" : "111a", "light_pad" : "26", "lights" : "on", "CREATE_DATE" : ISODate("2012-04-08T03:12:00Z"), "Department" : "Computer Science and Engg", "Percentage" : "7%", "Address" : { "Street" : "Burkit ", "City" : "vizag", "State" : "Tamil Nadu" }, "Gender" : "female" }
{ "_id" : ObjectId("5a7c1f5d7826eaca4b4e439d"), "firstName" : "kalu", "secName" : "ramana", "userId" : "111b/c", "light_pad" : "25", "lights" : "off", "CREATE_DATE" : ISODate("2014-06-08T03:12:00Z"), "Department" : "maths", "Percentage" : "46%", "Address" : { "Street" : "Burkit ", "City" : "bhimavaram", "State" : "Tamil Nadu" }, "Gender" : "male" }
{ "_id" : ObjectId("5a7c1fb37826eaca4b4e439e"), "firstName" : "praveen", "secName" : "pani", "userId" : "111b/c", "light_pad" : "52", "lights" : "on", "CREATE_DATE" : ISODate("2016-06-08T03:12:00Z"), "Department" : "maths", "Percentage" : "36%", "Address" : { "Street" : "vin ", "City" : "palakoderu", "State" : "Tamil Nadu" }, "Gender" : "male" }
{ "_id" : ObjectId("5a7c20057826eaca4b4e439f"), "firstName" : "vani", "secName" : "karun", "userId" : "111b/c", "light_pad" : "52", "lights" : "on", "CREATE_DATE" : ISODate("2013-06-08T03:12:00Z"), "Department" : "maths", "Percentage" : "76%", "Address" : { "Street" : "bali ", "City" : "srikakulam", "State" : "Tamil Nadu" }, "Gender" : "male" }
Any answer will be appreciated
Thanks in advance.

Answer 1

I don't understand your question properly, but I have a solution that could be related to your question. I hope it will help you.
db.test.aggregate([{
$match: {
_id: {
$in: [ObjectId("5a7c1d167826eaca4b4e4398"),
ObjectId("5a7c1db77826eaca4b4e4399")]
},
light_pad: {
$eq: "20"
}
}
}]);
It will gives the given result:
{
"_id" : ObjectId("5a7c1d167826eaca4b4e4398"),
"firstName" : "varun",
"secName" : "raju",
"userId" : "111a",
"light_pad" : "20",
"lights" : "on",
"CREATE_DATE" : ISODate("2018-05-08T03:12:00.000Z"),
"Department" : "Computer Science and Engg",
"Percentage" : "76%",
"Address" : {
"Street" : "Burkit Road",
"City" : "chennai",
"State" : "Tamil Nadu"
},
"Gender" : "Male"
}