Spider effect custo

Spider.js

            // No spider effect until zoom 18
            if (this.map.zoom < 18) {
                return;
            }

            // Group markers by position
            var groups = _.groupBy(this.map.markers, function (marker) {
                return marker.latitude + ';' + marker.longitude;
            });

            // Offsets
            var lngOffset = 0.0001;
            var latOffset = 0.00006;

            if (this.map.zoom === 22) {
                lngOffset = 0.00005;
                latOffset = 0.00003;
            }

            // Move markers at the same position on a circle having for center the common position
            _.forEach(groups, function (group) {
                if (group.length > 1) {

                    _.forEach(group, function (marker, index) {
                        // Compute new position
                        var longitude = marker.longitude + lngOffset * Math.cos(2 * Math.PI / group.length * (index + 1));
                        var latitude  = marker.latitude + latOffset * Math.sin(2 * Math.PI / group.length * (index + 1));

                        // Add polyline between old and new position
                        this.map.polylines.push([
                            { lat: marker.latitude, lng: marker.longitude },
                            { lat: latitude, lng: longitude }
                        ]);

                        // Set new position on marker
                        marker.longitude = longitude;
                        marker.latitude  = latitude;
                    }.bind(this))

                }
            }.bind(this));