Get city blocks by coordinates

city-blocks.js

const fetch = require('node-fetch'),
  polygonize = require('polygonize'),
  interpreterUrl = 'http://overpass-api.de/api/interpreter';

function buildOverpassQL(lat, lon, around='500') {
  return '[out:json];(' +
    ['primary', 'secondary', 'tertiary', 'residential', 'trunk'].map(
      e => `way["highway"="${e}"](around:${around}, ${lat}, ${lon});`
    ).join('')+'); out body; >; out skel qt;';
}

function toGeoJson(json) {
  const nodes = json.elements.reduce((prev, now) => {
    if (now.type == 'node')
      prev[now.id] = now;
    return prev;
  }, {});

  const createFeature = (start, end) => {
    const getCoordinates = id => [ nodes[id].lon, nodes[id].lat ];
    return {
      type: 'Feature',
      properties: {},
      geometry: {
        type: 'LineString',
        coordinates: [getCoordinates(start), getCoordinates(end)],
      }
    }
  };

  let geoJson = {
    type: 'FeatureCollection',
    features: [],
  };

  json.elements.forEach(e => {
    if (e.type != 'way')
      return;

    for (let i=0; i < e.nodes.length -1; i++) {
      geoJson.features.push(createFeature(e.nodes[i], e.nodes[i+1]));
    }
  });

  return geoJson;
}

fetch(interpreterUrl, { method: 'POST', body: `data=${encodeURIComponent(buildOverpassQL('40.798678','-73.966542', 200))}`})
  .then(res => res.json())
  .then(json => toGeoJson(json))
  .then(geoJson => polygonize(geoJson))
  .then(geoJson => console.log(JSON.stringify(geoJson)));