clustering.js

var fs = require('fs'),
    L = require('./leaflet');

function cluster(zoom, callback) {
    callback = callback || function () {};
    
    fs.readFile('sample-data.geojson', function (err, content) {
        var data = JSON.parse(content);
        
        var map = L.map('map', {
                center: [38.543869175876154, -92.5433349609375],
                zoom: zoom,
                maxZoom: 12
            }),
            
            dataLayer = L.geoJson(data),
            clusterLayer = new L.MarkerClusterGroup();
        
        map.addLayer(clusterLayer);
        clusterLayer.addLayer(dataLayer);
        
        var features = clusterLayer._featureGroup.getLayers().map(function (cluster) {
            var f = cluster.toGeoJSON();
            f.properties.featureCount = cluster.__parent.getChildCount();
            return f;
        });
        
        callback({
            type: "FeatureCollection",
            features: features
        });
    });
}

if (require.main === module) {
    cluster(9, function (geojson) {
        process.stdout.write(JSON.stringify(geojson));  
    });
} else {
    module.exports = cluster;
}