Scale Line

Example of a scale line.

<!DOCTYPE html>
<html>
  <head>
    <title>Scale Line</title>
    <link rel="stylesheet" href="https://openlayers.org/en/v5.1.3/css/ol.css" type="text/css">
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>

  </head>
  <body>
    <div id="map" class="map"></div>
    <select id="units">
      <option value="degrees">degrees</option>
      <option value="imperial">imperial inch</option>
      <option value="us">us inch</option>
      <option value="nautical">nautical mile</option>
      <option value="metric" selected>metric</option>
    </select>
    <script>
      import Map from 'ol/Map.js';
      import View from 'ol/View.js';
      import {defaults as defaultControls, ScaleLine} from 'ol/control.js';
      import TileLayer from 'ol/layer/Tile.js';
      import OSM from 'ol/source/OSM.js';


      var scaleLineControl = new ScaleLine();

      var map = new Map({
        controls: defaultControls({
          attributionOptions: {
            collapsible: false
          }
        }).extend([
          scaleLineControl
        ]),
        layers: [
          new TileLayer({
            source: new OSM()
          })
        ],
        target: 'map',
        view: new View({
          center: [0, 0],
          zoom: 2
        })
      });


      var unitsSelect = document.getElementById('units');
      function onChange() {
        scaleLineControl.setUnits(unitsSelect.value);
      }
      unitsSelect.addEventListener('change', onChange);
      onChange();
    </script>
  </body>
</html>