turf.js

Example on how to use turf.js with OpenLayers.

Example showing the integration of turf.js with OpenLayers. The turf.js function along is used to display a marker every 200 meters along a street.

main.js

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 {along} from '@turf/along';
import {fromLonLat} from 'ol/proj.js';
import {length} from '@turf/length';

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 lineLength = length(turfLine, 'kilometers');
    for (let i = 1; i <= lineLength / distance; i++) {
      const turfPoint = 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,
  }),
});

index.html

<!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>

    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "turf",
  "dependencies": {
    "ol": "10.3.1",
    "@turf/along": "^7.1.0",
    "@turf/length": "^7.1.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}