Mongoose Query: Find an element inside an array

Using the $ positional operator, you can get the results. However, if you have multiple elements in the vehicles array all of them will be returned in the result, as you can only use one positional operator in the projection and you are working with 2 arrays (one inside another).

I would suggest you take a look at the aggregation framework, as you'll get a lot more flexibility. Here's an example query for your question that runs in the shell. I'm not familiar with mongoose, but I guess this will still help you and you'd be able to translate it:

db.collection.aggregate([    // Get only the documents where "email" equals "test@test.com" -- REPLACE with params.username    {"$match" : {email : "test@test.com"}},     // Unwind the "inventories" array    {"$unwind" : "$inventories"},     // Get only elements where "inventories.title" equals "activeInventory"    {"$match" : {"inventories.title":"activeInventory"}},     // Unwind the "vehicles" array    {"$unwind" : "$inventories.vehicles"},     // Filter by vehicle ID -- REPLACE with vehicleID     {"$match" : {"inventories.vehicles._id":ObjectId("53440e94c02b3cae81eb0069")}},     // Tidy up the output    {"$project" : {_id:0, vehicle:"$inventories.vehicles"}}])

This is the output you'll get:

{        "result" : [                {                        "vehicle" : {                                "_id" : ObjectId("53440e94c02b3cae81eb0069"),                                "tags" : [                                        "vehicle"                                ],                                "details" : [                                        {                                                "_id" : ObjectId("53440e94c02b3cae81eb0066"),                                                "year" : 2007,                                                "transmission" : "Manual",                                                "price" : 1000,                                                "model" : "Firecar",                                                "mileageReading" : 50000,                                                "make" : "Bentley",                                                "interiorColor" : "blue",                                                "history" : "CarProof",                                                "exteriorColor" : "blue",                                                "driveTrain" : "SWD",                                                "description" : "test vehicle",                                                "cylinders" : 4,                                                "mileageType" : "kms"                                        }                                ]                        }                }        ],        "ok" : 1}

getting the chaining query format ... i dont know how to parse it but, what you are searching for is projection, you should take a look to http://docs.mongodb.org/manual/reference/operator/projection/

it would probably look like this :

user.findOne({email: params.username}, {'inventories.title': {$elemMatch: "activeInventory", 'invertories.vehicle.id': $elemMatch: params.vehicleId}, function(err, result) {    console.log(err);    console.log(result);})