MongoDB Geospatial Querys

//example data
db.venues.insert( {
  name: "Central Park",
  location: { type: "Point", coordinates: [ -73.97, 40.77 ] },
  category: "Parks"
} );
db.venues.insert( {
  name: "Sara D. Roosevelt Park",
  location: { type: "Point", coordinates: [ -73.9928, 40.7193 ] },
  category: "Parks"
} );
db.venues.insert( {
  name: "Polo Grounds",
  location: { type: "Point", coordinates: [ -73.9375, 40.8303 ] },
  category: "Stadiums"
} );

//using a 2dsphere index
db.venues.createIndex( { location: "2dsphere" } )

// method as promise to find an array of venues
// near a `point {long, lat}` 
// within certain `radius` in the specified `unit`
// with 'km' as the default unit
findNearVenuesWithinRadius(point, radius, unit = 'km') {
  const earthRadius = {
    km: 6378.1, // Kilometers
    mi: 3963.2, // Miles
  };
  const query = {
    location: {
      $geoWithin: {
        $centerSphere: [ [ point.long, point.lat ], radius / earthRadius[unit] ] ] 
      }
    }
  };
  // the `toArray` method returns a Promise when Callback is not provided
  return db.venues.find(query).toArray();
}