[nodejs] Node.js how to pass geojson from mongodb to object I can use in frontend

[Artur Tochowicz]

down votefavorite 
<http://stackoverflow.com/questions/37890077/node-js-how-to-pass-geojson-from-mongodb-to-object-i-can-use-in-frontend#>

I am trying to cluster 5m points stored in mongoDB. Maximum result from 1 
query is currently just around 1m so I have decided to use: PruneCluster 
<https://github.com/SINTEF-9012/PruneCluster> for first visuals. Points are 
stored as geoJSON object and there is an 2dsphere index on them.

I connect to mongodb using native node.js driver and query to find points 
within a polygon, that will only return loc field from the collection and 
route result for preview:

router.get('/map', function(resq,res) {
  var MongoClient = mongodb.MongoClient;
  var url = 'mongodb://localhost:27017/airboost';

  MongoClient.connect(url, function(err, db) {
    if(err){
      console.log('Unable to connect to db ', err);
    } else {
        console.log('Connected!!!');

        var collection = db.collection('listingsF');

        collection.find({
           loc: {
             $geoWithin: {
                $geometry: {
                   type : "Polygon" ,
                       coordinates: 
[[[121.48521363894814,31.41360430073249],[...],[121.48865692654915,31.41168940543709]]]
                            }
                          }
                }
          },{loc:1}).toArray(function(err, result){

          if (err) {
            res.send(err);
          } else if (result.length) {
            res.send(result);
          } else {
            res.send('Nothing found');
          }
          db.close();
        });
      }
  });});

I get a list of objects like this:

[
  {
    "_id": "567f972bad55ac0797baa75b",
    "loc": {
      "type": "Point",
      "coordinates": [
        -85.84556526181,
        10.29620625503
      ]
    }
  },
  {
    "_id": "567f972bad55ac0797baa75c",
    "loc": {
      "type": "Point",
      "coordinates": [
        -54.943878777465,
        -34.964002797642
      ]
    }
  }]

Then I need to pass that result somehow to function in script from /public 
folder, So I can display the cluster on leaflet map:

var pruneCluster = new PruneClusterForLeaflet();
  ... var marker = new PruneCluster.Marker(latitude, longitude);
pruneCluster.RegisterMarker(marker);
  ... 
leafletMap.addLayer(pruneCluster);

I can print content with jade anyway I want, but have no idea how to pass 
all that mongodb data as Markers to PruneCluster. I don't need full code 
just a point to a direction. Can someone help me?

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