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 'ol/ol.css';
import Map from 'ol/Map';
import TopoJSON from 'ol/format/TopoJSON';
import VectorSource from 'ol/source/Vector';
import View from 'ol/View';
import XYZ from 'ol/source/XYZ';
import {Fill, Stroke, Style} from 'ol/style';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';

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 XYZ({
    attributions: attributions,
    url: 'https://api.maptiler.com/maps/darkmatter/{z}/{x}/{y}.png?key=' + key,
    tileSize: 512,
  }),
});

const style = new Style({
  fill: new Fill({
    color: 'rgba(255, 255, 255, 0.6)',
  }),
  stroke: new Stroke({
    color: '#319FD3',
    width: 1,
  }),
});

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: style,
});

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>
    <!-- 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>
    <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": "topojson",
  "dependencies": {
    "ol": "6.13.1-dev"
  },
  "devDependencies": {
    "parcel": "^2.0.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}