JSTS Integration

main.js

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

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>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>

    <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/jsts.min.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "jsts",
  "dependencies": {
    "ol": "10.2.1"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}