geojson-bounding-box/geojson-bounding-box.js

Efficiently computes a GeoJSON's bounding box.

/**
 * geojson-bounding-box v0.2.0
 * Efficiently computes a GeoJSON's bounding box.
 *
 * @author Daniel Pulido <dpmcmlxxvi@gmail.com>
 * @license MIT
 * @preserve
 */

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
  typeof define === 'function' && define.amd ? define(factory) :
  (global = global || self, global.GeojsonBoundingBox = factory());
}(this, function () { 'use strict';

  /**
   * @description Create input GeoJSON bounding box.
   * @param {GeoJSON} geojson Input GeoJSON.
   * @return {Array} GeoJSON bounding box.
   */
  var github = function(geojson) {
    const bbox = [
      Number.POSITIVE_INFINITY,
      Number.POSITIVE_INFINITY,
      Number.POSITIVE_INFINITY,
      Number.NEGATIVE_INFINITY,
      Number.NEGATIVE_INFINITY,
      Number.NEGATIVE_INFINITY,
    ];

    // Update bbox with each coordinate
    let dimensions = 2;
    for (const coordinate of coordEach(geojson)) {
      dimensions = Math.max(dimensions, coordinate.length);
      for (let i = 0; i < coordinate.length; ++i) {
        const j = 3 + i;
        bbox[i] = Math.min(bbox[i], coordinate[i]);
        bbox[j] = Math.max(bbox[j], coordinate[i]);
      }
    }

    // Remove 3rd dimension if not present in data.
    if (dimensions !== 3) {
      return [bbox[0], bbox[1], bbox[3], bbox[4]];
    }
    return bbox;
  };

  /**
   * @description Generator that yields each GeoJSON coordinate.
   * @param {GeoJSON} geojson Input GeoJSON.
   * @yields [Array] GeoJSON 2D or 3D coordinate.
   */
  function* coordEach(geojson) {
    switch (geojson.type) {
      case 'Point':
        yield geojson.coordinates;
        break;
      case 'LineString':
      case 'MultiPoint':
        yield* geojson.coordinates;
        break;
      case 'Polygon':
      case 'MultiLineString':
        for (const part of geojson.coordinates) {
          yield* part;
        }
        break;
      case 'MultiPolygon':
        for (const polygon of geojson.coordinates) {
          for (const ring of polygon) {
            yield* ring;
          }
        }
        break;
      case 'GeometryCollection':
        for (const geometry of geojson.geometries) {
          yield* coordEach(geometry);
        }
        break;
      case 'FeatureCollection':
        for (const feature of geojson.features) {
          yield* coordEach(feature);
        }
        break;
      default:
        yield* coordEach(geojson.geometry);
    }
  }

  return github;

}));