reduce.js

'use strict';

var tileReduce = require('tile-reduce');
var path = require('path');

var numFeatures = 0;

tileReduce({
  //test bbox area
  bbox: [-77.033, 36.855, -76.073, 37.468],
  // mapbox qa tiles are done at zoom 12
  zoom: 12,
  //__dirname is a magic variable the node knows what to do with
  map: path.join(__dirname, './map.js'),
  sources: [{name: 'osm', mbtiles: path.join(__dirname, './usa.mbtiles'), raw: false}]
})
.on('reduce', function(num) {
  numFeatures += num;
})
.on('end', function() {
  console.log('Features total: %d', numFeatures);
});