Merge polygons and exclude holeless, self-intersecting polygons

geo-merge-holeless.js

const assert = require('assert');
const polygon = require('turf-polygon');
const point = require('turf-point');
const { default: distance } = require('@turf/distance');
const { default: union } = require('@turf/union');
const difference = require('@turf/difference');

const merge = (polygons) => polygons.reduce((p, c) => union(p, polygon([c])), polygon([]));

const normalize = (poly, ...holes) => [holes.reduce((p, h) => {
  let dist = Number.MAX_VALUE;
  let closest = [0, 0];
  for (let x = 0; x < p.length - 1; x += 1) {
    const ptX = point(p[x]);
    for (let y = 0; y < h.length - 1; y += 1) {
      const distNew = distance(ptX, point(h[y]));
      if (dist > distNew) {
        closest = [x, y];
        dist = distNew;
      }
    }
  }
  const r = [
    ...p.slice(closest[0], -1),
    ...p.slice(0, closest[0] + 1),
    ...h.slice(closest[1]),
    ...h.slice(1, closest[1] + 1),
    p[closest[0]]
  ];
  return r;
}, poly)];

const combine = (include, exclude) => {
  const plus = merge(include);
  const minus = merge(exclude);
  const { geometry } = difference(plus, minus);
  if (geometry.type === 'MultiPolygon') {
    return geometry.coordinates.map((poly) => normalize(...poly));
  }
  assert(geometry.type === 'Polygon');
  return [normalize(...geometry.coordinates)];
};

const coordinates = combine([
  [[-3.0322265625, 25.58208527870072], [0.9667968749999999, 25.58208527870072], [0.9667968749999999, 28.05259082333983], [-3.0322265625, 28.05259082333983], [-3.0322265625, 25.58208527870072]],
  [[-4.130859375, 12.897489183755892], [13.271484375, 12.897489183755892], [13.271484375, 22.917922936146045], [-4.130859375, 22.917922936146045], [-4.130859375, 12.897489183755892]],
  [[8.0859375, 21.289374355860424], [16.083984375, 21.289374355860424], [16.083984375, 26.667095801104814], [8.0859375, 26.667095801104814], [8.0859375, 21.289374355860424]]
], [
  [[-8.876953125, 19.228176737766262], [-0.17578125, 19.228176737766262], [-0.17578125, 26.115985925333536], [-8.876953125, 26.115985925333536], [-8.876953125, 19.228176737766262]],
  [[2.197265625, 15.876809064146757], [5.9765625, 15.876809064146757], [5.9765625, 18.729501999072138], [2.197265625, 18.729501999072138], [2.197265625, 15.876809064146757]],
  [[6.328125, 19.9526963975442], [8.1298828125, 19.9526963975442], [8.1298828125, 21.49396356306447], [6.328125, 21.49396356306447], [6.328125, 19.9526963975442]],
  [[7.84423828125, 16.636191878397664], [9.31640625, 16.636191878397664], [9.31640625, 18.020527657852337], [7.84423828125, 18.020527657852337], [7.84423828125, 16.636191878397664]],
  [[0.54931640625, 18.60460138845525], [1.494140625, 18.60460138845525], [1.494140625, 19.37334071336406], [0.54931640625, 19.37334071336406], [0.54931640625, 18.60460138845525]],
  [[2.70263671875, 19.456233596018], [3.8671874999999996, 19.456233596018], [3.8671874999999996, 20.571081893508193], [2.70263671875, 20.571081893508193], [2.70263671875, 19.456233596018]],
  [[4.482421875, 20.612219573881042], [5.4052734375, 20.612219573881042], [5.4052734375, 21.350781150679737], [4.482421875, 21.350781150679737], [4.482421875, 20.612219573881042]],
  [[11.074218749999998, 13.624633438236152], [12.50244140625, 13.624633438236152], [12.50244140625, 14.753635331540442], [11.074218749999998, 14.753635331540442], [11.074218749999998, 13.624633438236152]]
]);

console.log(JSON.stringify({
  type: 'Feature',
  properties: {},
  geometry: { type: 'MultiPolygon', coordinates }
}));