TopoJSON

Demonstrates rendering of features from a TopoJSON topology.

This example uses a vector layer with ol/format/TopoJSON for rendering features from TopoJSON.

main.js

import Map from 'ol/Map.js';
import View from 'ol/View.js';
import TopoJSON from 'ol/format/TopoJSON.js';
import TileLayer from 'ol/layer/Tile.js';
import VectorLayer from 'ol/layer/Vector.js';
import ImageTile from 'ol/source/ImageTile.js';
import VectorSource from 'ol/source/Vector.js';

const key = 'Get your own API key at https://www.maptiler.com/cloud/';
const attributions =
  '<a href="https://www.maptiler.com/copyright/" target="_blank">&copy; MapTiler</a> ' +
  '<a href="https://www.openstreetmap.org/copyright" target="_blank">&copy; OpenStreetMap contributors</a>';

const raster = new TileLayer({
  source: new ImageTile({
    attributions: attributions,
    url:
      'https://api.maptiler.com/maps/dataviz-dark/{z}/{x}/{y}.png?key=' + key,
    tileSize: 512,
  }),
});

const vector = new VectorLayer({
  source: new VectorSource({
    url: 'data/topojson/world-110m.json',
    format: new TopoJSON({
      // don't want to render the full world polygon (stored as 'land' layer),
      // which repeats all countries
      layers: ['countries'],
    }),
    overlaps: false,
  }),
  style: {
    'stroke-color': 'white',
    'stroke-width': 1.5,
  },
});

const map = new Map({
  layers: [raster, vector],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 1,
  }),
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>TopoJSON</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": "topojson",
  "dependencies": {
    "ol": "10.5.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}