JSTS Integration

Example on how to use JSTS with OpenLayers.

Example showing the integration of JSTS with OpenLayers.

main.js

import 'ol/ol.css';
import GeoJSON from 'ol/format/GeoJSON';
import LinearRing from 'ol/geom/LinearRing';
import Map from 'ol/Map';
import OSM from 'ol/source/OSM';
import VectorSource from 'ol/source/Vector';
import View from 'ol/View';
import {
  LineString,
  MultiLineString,
  MultiPoint,
  MultiPolygon,
  Point,
  Polygon,
} from 'ol/geom';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';
import {fromLonLat} from 'ol/proj';

const source = new VectorSource();
fetch('data/geojson/roads-seoul.geojson')
  .then(function (response) {
    return response.json();
  })
  .then(function (json) {
    const format = new GeoJSON();
    const features = format.readFeatures(json, {
      featureProjection: 'EPSG:3857',
    });

    const parser = new jsts.io.OL3Parser();
    parser.inject(
      Point,
      LineString,
      LinearRing,
      Polygon,
      MultiPoint,
      MultiLineString,
      MultiPolygon
    );

    for (let i = 0; i < features.length; i++) {
      const feature = features[i];
      // convert the OpenLayers geometry to a JSTS geometry
      const jstsGeom = parser.read(feature.getGeometry());

      // create a buffer of 40 meters around each line
      const buffered = jstsGeom.buffer(40);

      // convert back from JSTS and replace the geometry on the feature
      feature.setGeometry(parser.write(buffered));
    }

    source.addFeatures(features);
  });
const vectorLayer = new VectorLayer({
  source: source,
});

const rasterLayer = new TileLayer({
  source: new OSM(),
});

const map = new Map({
  layers: [rasterLayer, vectorLayer],
  target: document.getElementById('map'),
  view: new View({
    center: fromLonLat([126.979293, 37.528787]),
    zoom: 15,
  }),
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>JSTS Integration</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <!-- The lines below are only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,TextDecoder"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/core-js/3.18.3/minified.js"></script>
    <script src="https://unpkg.com/jsts@2.3.0/dist/jsts.min.js"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "jsts",
  "dependencies": {
    "ol": "6.13.1-dev"
  },
  "devDependencies": {
    "parcel": "^2.0.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}