How to display polygons that are within a specific range (circle) using Leaflet - mongodb

Question

I am trying find a solution on how to display polygons that are only within a specific range, a circle with radius using leaflet.
Polygons screenshots
Before, I have ask for help regarding on the display of points within a specific range but this time, since a polygon have many nodes/coordinates, i don't have any idea of how it can be done for polygons; a foreach statement?
Any solution? Thanks for the help!
Similar problem solved for displaying points within a specific range

Answer 1

Since you're using MongoDB, the best solution here is (if that's possible), to handle this in the database. Put 2dsphere indexes on your document's loc field and use a $geoWithin query in combination with $centerSphere:
The following example queries grid coordinates and returns all documents within a 10 mile radius of longitude 88 W and latitude 30 N. The query converts the distance to radians by dividing by the approximate radius of the earth, 3959 miles:
db.places.find( {
loc: { $geoWithin: { $centerSphere: [ [ -88, 30 ], 10/3959 ] } }
} )
2dsphere reference: http://docs.mongodb.org/manual/core/2dsphere/
$geoWithin reference: http://docs.mongodb.org/manual/reference/operator/query/geoWithin/
$centerSphere reference: http://docs.mongodb.org/manual/reference/operator/query/centerSphere/
If you really want to do this clientside (which i absolutely wouldn't recommend) and you don't want to build your on solution (which is possible) you could take a look at GeoScript.
GeoScript's geom.Geometry() class has a contains method:
Tests if this geometry contains the other geometry (without boundaries touching).
Geom.geometry reference: http://geoscript.org/js/api/geom/geometry.html
EDIT: Here's the pure JS/Leaflet solution as requested in the comments, this is quick-n-dirty, but it should work. Here the containsPolygon method returns true when all of the polygon's points are within the circle:
L.Circle.include({
'containsPoint': function (latLng) {
return this.getLatLng().distanceTo(latLng) < this.getRadius();
},
'containsPolygon': function (polygon) {
var results = [];
polygon.getLatLngs().forEach(function (latLng) {
results.push(this.containsPoint(latLng));
}, this);
return (results.indexOf(false) === -1);
}
});
Here's a working example: http://plnkr.co/edit/JlFToy?p=preview
If you want to return true if one or more of the polygon's points are within the circle than you must change the return statement to this:
return (results.indexOf(true) !== -1);