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Vector Layer

vector63 geojson8

 

Example of a countries vector layer with country information.

The countries are loaded from a GeoJSON file. Information about countries is shown on hover and click.

main.js
import 'ol/ol.css';
import GeoJSON from 'ol/format/GeoJSON';
import Map from 'ol/Map';
import VectorLayer from 'ol/layer/Vector';
import VectorSource from 'ol/source/Vector';
import View from 'ol/View';
import {Fill, Stroke, Style, Text} from 'ol/style';

const style = new Style({
  fill: new Fill({
    color: 'rgba(255, 255, 255, 0.6)',
  }),
  stroke: new Stroke({
    color: '#319FD3',
    width: 1,
  }),
  text: new Text({
    font: '12px Calibri,sans-serif',
    fill: new Fill({
      color: '#000',
    }),
    stroke: new Stroke({
      color: '#fff',
      width: 3,
    }),
  }),
});

const vectorLayer = new VectorLayer({
  source: new VectorSource({
    url: 'data/geojson/countries.geojson',
    format: new GeoJSON(),
  }),
  style: function (feature) {
    style.getText().setText(feature.get('name'));
    return style;
  },
});

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

const highlightStyle = new Style({
  stroke: new Stroke({
    color: '#f00',
    width: 1,
  }),
  fill: new Fill({
    color: 'rgba(255,0,0,0.1)',
  }),
  text: new Text({
    font: '12px Calibri,sans-serif',
    fill: new Fill({
      color: '#000',
    }),
    stroke: new Stroke({
      color: '#f00',
      width: 3,
    }),
  }),
});

const featureOverlay = new VectorLayer({
  source: new VectorSource(),
  map: map,
  style: function (feature) {
    highlightStyle.getText().setText(feature.get('name'));
    return highlightStyle;
  },
});

let highlight;
const displayFeatureInfo = function (pixel) {
  const feature = map.forEachFeatureAtPixel(pixel, function (feature) {
    return feature;
  });

  const info = document.getElementById('info');
  if (feature) {
    info.innerHTML = feature.getId() + ': ' + feature.get('name');
  } else {
    info.innerHTML = ' ';
  }

  if (feature !== highlight) {
    if (highlight) {
      featureOverlay.getSource().removeFeature(highlight);
    }
    if (feature) {
      featureOverlay.getSource().addFeature(feature);
    }
    highlight = feature;
  }
};

map.on('pointermove', function (evt) {
  if (evt.dragging) {
    return;
  }
  const pixel = map.getEventPixel(evt.originalEvent);
  displayFeatureInfo(pixel);
});

map.on('click', function (evt) {
  displayFeatureInfo(evt.pixel);
});
index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Vector Layer</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <!-- The line below is 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,URL,TextDecoder,Number.isInteger"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <div id="info">&nbsp;</div>
    <script src="main.js"></script>
  </body>
</html>
package.json
{
  "name": "vector-layer",
  "dependencies": {
    "ol": "6.6.1"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}