GeoJSON Layer

<!--
  示例：GeoJSON 数据源标注
  要点：ol.format.GeoJSON 解析内联数据，featureProjection 把经纬度转成 EPSG:3857
  依赖：OpenLayers 10.3.1 · jsDelivr CDN
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta name="robots" content="noindex,follow">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>GeoJSON 数据源标注</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/ol@10.3.1/ol.css">
<style>
  html,body{height:100%;margin:0}
  body{display:flex;flex-direction:column;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:12px;align-items:center;font-size:12px;color:#58606e}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar"><span id="info">解析中…</span></div>
<div id="map"></div>
<script src="https://cdn.jsdelivr.net/npm/ol@10.3.1/dist/ol.js"></script>
<script>
(function () {
  'use strict';

  if (typeof ol === 'undefined') {
    document.getElementById('map').innerHTML =
      '<div style="padding:20px;color:#b42318">OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  /* 页面内联的 GeoJSON，坐标为经纬度 */
  var geojson = {
    type: 'FeatureCollection',
    features: [
      {
        type: 'Feature',
        properties: { name: '西湖北区' },
        geometry: {
          type: 'Polygon',
          coordinates: [[[120.132, 30.248], [120.156, 30.250], [120.158, 30.268], [120.136, 30.266], [120.132, 30.248]]]
        }
      },
      {
        type: 'Feature',
        properties: { name: '西湖南区' },
        geometry: {
          type: 'Polygon',
          coordinates: [[[120.140, 30.222], [120.163, 30.224], [120.162, 30.240], [120.142, 30.238], [120.140, 30.222]]]
        }
      },
      {
        type: 'Feature',
        properties: { name: '湖心岛' },
        geometry: {
          type: 'Polygon',
          coordinates: [[[120.144, 30.238], [120.151, 30.238], [120.151, 30.244], [120.144, 30.244], [120.144, 30.238]]]
        }
      }
    ]
  };

  var features = new ol.format.GeoJSON().readFeatures(geojson, {
    featureProjection: 'EPSG:3857'
  });

  var layer = new ol.layer.Vector({
    source: new ol.source.Vector({ features: features })
  });

  /* 用属性 name 作为面标注 */
  layer.setStyle(function (feature) {
    return new ol.style.Style({
      fill: new ol.style.Fill({ color: 'rgba(31, 95, 208, 0.28)' }),
      stroke: new ol.style.Stroke({ color: '#1f5fd0', width: 2 }),
      text: new ol.style.Text({
        text: feature.get('name'),
        font: '600 12px sans-serif',
        fill: new ol.style.Fill({ color: '#16181d' }),
        stroke: new ol.style.Stroke({ color: '#ffffff', width: 3 })
      })
    });
  });

  new ol.Map({
    target: 'map',
    layers: [
      new ol.layer.Tile({ source: new ol.source.XYZ({url: 'https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/{z}/{y}/{x}', attributions: 'Tiles © Esri'}) }),
      layer
    ],
    view: new ol.View({
      center: ol.proj.fromLonLat([120.148, 30.245]),
      zoom: 13
    }),
    controls: ol.control.defaults.defaults({ attribution: false })
  });

  document.getElementById('info').textContent =
    'GeoJSON 面要素 ' + layer.getSource().getFeatures().length + ' 个';
})();
</script>
</body>
</html>