MongoDB aggregate, geNear and iterate over callback - node.js

Question

I have a problem and I can´t find a solution. I have some MongoSchemas where I store Geolocation from users. Mobile Phone is sending me longitude and latitude every 5 minutes. This API is working perfectly.
Mongo-Schema looks like:
// Importing Node packages required for schema
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
//= ===============================
// User Schema
//= ===============================
const GeolocationSchema = new Schema({
loc: {
type: { type: String },
coordinates: { type: [Number], index: '2dsphere' }
},
user: { type: Schema.Types.ObjectId, ref: 'User' }
},
{
timestamps: true
});
module.exports = mongoose.model('Geolocation', GeolocationSchema);
Now, I want to calculate users-nearby which have an "updateAt"-timestamp not even longer than 5 minutes in the past. That means that one or more users can be in a distance of e.g. 500m until 5 minutes in the past. This should be a match. For this I use Mongo aggregate, and I want to iterate the callback-result and extract the user._id out of the result to build a match.
This is what I tried:
const Geolocation = require('../models/geolocation')
User = require('../models/user'),
config = require('../config/main');
exports.setGeolocation = function (req, res, next) {
// Only return one message from each conversation to display as snippet
console.log(req.user._id);
var geoUpdate = Geolocation.findOneAndUpdate( { user: req.user._id },
{ loc: {
type: 'Point',
coordinates: req.body.coordinates.split(',').map(Number)
},
user: req.user._id
},
{upsert: true, new: true, runValidators: true}, // options
function (err, doc) { // callback
if (err) {
console.log(err);
}
});
// create dates for aggregate query
var toDate = new Date( (new Date()).getTime());
var fromDate = new Date( (new Date()).getTime() - 5000 * 60 );
var match = Geolocation.aggregate([
{
$geoNear: {
near: {
type: "Point",
coordinates: req.body.coordinates.split(',').map(Number)
},
distanceField: "dist.calculated",
maxDistance: 500,
includeLocs: "dist.location",
uniqueDocs: true,
query: { user: {$ne: req.user._id } , updatedAt: { $gte: fromDate,$lte: toDate }},
num: 5,
spherical: true
}
}], function (err, doc){
//here I´m going in trouble correctly parsing doc
var str = JSON.stringify(doc);
var newString = str.substring(1, str.length-1);
var response = JSON.parse(newString);
console.log(response.user);
});
res.sendStatus(200);
};
As you can see I´m going in trouble in parsing the "doc"-callback to iterate over the documents. If I want to parse it as jSON I´m getting an token-error on position 1. If I have more than 2 results, I´m getting an error on position 288.
That´s why I tried to parse and stringify the "doc". But this is not working correctly.
Maybe, someone could help me with a solution. I´m not familiar with mongo-functions because I´m starting with it, maybe there is a better solution but I can´t find something else to calculate geoNear and iterate afterwards over the results.
Thx at all who can help...