Style Function

<!--
  示例：属性驱动样式
  要点：setStyle 传入函数，按 level 属性返回不同半径与颜色的 ol.style.Style
  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>属性驱动样式</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:14px;align-items:center;font-size:12px;color:#58606e}
  .dot{display:inline-block;width:8px;height:8px;border-radius:50%;margin-right:4px}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <span><i class="dot" style="background:#1f5fd0"></i>一级</span>
  <span><i class="dot" style="background:#d97706"></i>二级</span>
  <span><i class="dot" style="background:#c0392b"></i>三级</span>
  <span>圆点半径随等级递增</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;
  }

  var palette = { 1: '#1f5fd0', 2: '#d97706', 3: '#c0392b' };
  var radius = { 1: 5, 2: 8, 3: 11 };

  var raw = [
    [116.3800, 39.9005, '西单', 3],
    [116.3912, 39.9074, '天安门', 1],
    [116.4106, 39.9147, '王府井', 2],
    [116.4200, 39.9220, '东四', 1],
    [116.3966, 39.9182, '景山', 2],
    [116.4068, 39.9040, '崇文门', 3],
    [116.3748, 39.9140, '复兴门', 2],
    [116.4130, 39.9088, '东单', 1]
  ];

  var features = raw.map(function (p) {
    return new ol.Feature({
      geometry: new ol.geom.Point(ol.proj.fromLonLat([p[0], p[1]])),
      name: p[2],
      level: p[3]
    });
  });

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

  /* 样式函数：属性决定半径、颜色与标注 */
  layer.setStyle(function (feature) {
    var level = feature.get('level');
    return new ol.style.Style({
      image: new ol.style.Circle({
        radius: radius[level],
        fill: new ol.style.Fill({ color: palette[level] }),
        stroke: new ol.style.Stroke({ color: '#ffffff', width: 2 })
      }),
      text: new ol.style.Text({
        text: feature.get('name'),
        font: '500 11px sans-serif',
        offsetY: -(radius[level] + 6),
        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([116.397, 39.911]),
      zoom: 13
    }),
    controls: ol.control.defaults.defaults({ attribution: false })
  });
})();
</script>
</body>
</html>