原文链接及内容

原文链接：https://openlayers.org/en/latest/examples/turf.html

运行界面

此示例演示了如何在OpenLayers中使用turf.js库。这里使用turf.js库来实现沿街道每隔200米显示一个标记的效果。

main.js代码如下：

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import GeoJSON from 'ol/format/GeoJSON.js';
import Map from 'ol/Map.js';
import View from 'ol/View.js';
import {OSM, Vector as VectorSource} from 'ol/source.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);
    const street = features[0];

    // convert to a turf.js feature
    const turfLine = format.writeFeatureObject(street);

    // show a marker every 200 meters
    const distance = 0.2;

    // get the line length in kilometers
    const length = turf.lineDistance(turfLine, 'kilometers');
    for (let i = 1; i <= length / distance; i++) {
      const turfPoint = turf.along(turfLine, i * distance, 'kilometers');

      // convert the generated point to a OpenLayers feature
      const marker = format.readFeature(turfPoint);
      marker.getGeometry().transform('EPSG:4326', 'EPSG:3857');
      source.addFeature(marker);
    }

    street.getGeometry().transform('EPSG:4326', 'EPSG:3857');
    source.addFeature(street);
  });
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([126.980366, 37.52654]),
    zoom: 15,
  }),
});

界面布局文件index.html代码如下：

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>turf.js</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>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://cdn.jsdelivr.net/npm/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <script src="https://api.tiles.mapbox.com/mapbox.js/plugins/turf/v2.0.0/turf.min.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>