How to show data from 2 collections in Mongodb with DBRef

I have two main collections in my MongoDB, users & address. I am using '$ref' and '$id' in my 1st collection (users) to refer to documents of the 2nd collection (address). I want to write a query to show details of the user and his addresses.

This is my first collection 'users'. It has 1 document

{
    "_id" : ObjectId("52ffc33cd85242f436000001"),
    "contact" : "987654321",
    "dob" : "01-01-1991",
    "name" : "Tom Benzamin",
    "address" : [ 
        {
            "$ref" : "address",
            "$id" : ObjectId("534009e4d852427820000002"),
            "$db" : "test"
        }, 
        {
            "$ref" : "address",
            "$id" : ObjectId("52ffc4a5d85242602e000000"),
            "$db" : "test"
        }
    ]
}

This is my 2nd collection 'address'. It has 3 documents

{
    "_id" : ObjectId("52ffc4a5d85242602e000000"),
    "building" : "22 A, Indiana Apt",
    "pincode" : 123456.0000000000000000,
    "city" : "Los Angeles",
    "state" : "California"
},
{
    "_id" : ObjectId("52ffc4a5d85242602e000001"),
    "building" : "170 A, Acropolis Apt",
    "pincode" : 456789.0000000000000000,
    "city" : "Chicago",
    "state" : "Illinois"
},
{
    "_id" : ObjectId("534009e4d852427820000002"),
    "building" : "22 A, Indiana Apt",
    "pincode" : 123456.0000000000000000,
    "city" : "Los Angeles",
    "state" : "California"
}

I have write this code but it is not working. It show the word 'null' when I run it

var user = db.users.findOne({"name":"Tom Benzamin"})
var dbRef = user.address
db[dbRef.$ref].findOne({"_id":(dbRef.$id)})

It shows null because dbRef is an array:

 {
    "0" : {
        "$ref" : "address",
        "$id" : ObjectId("52ffc4a5d85242602e000000"),
        "$db" : "test"
    },
    "1" : {
        "$ref" : "address",
        "$id" : ObjectId("534009e4d852427820000002"),
        "$db" : "test"
    }
}

Try with this:

var user = db.users.findOne({"name":"Tom Benzamin"})
var dbRef = user.address
var ids = new Array();
for (i = 0; i < dbRef.length; i++){
    ids.push(dbRef[i].$id)
}
db[dbRef[0].$ref].find({"_id":{$in:ids}});