Filter Points Webgl

<!--
  说明：按属性过滤点要素
  核心逻辑：样式函数按分区与数值阈值返回 null 过滤，三千个点即时筛选
  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>按属性过滤点要素</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;flex-wrap:wrap}
  .bar button{font:inherit;padding:4px 10px;border:1px solid #c9d0da;border-radius:5px;
              background:#fff;color:#1f2a37;cursor:pointer}
  .bar button.on{background:#1f5fd0;border-color:#1f5fd0;color:#fff}
  .bar input[type=range]{width:120px}
  #info{margin-left:auto}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <button data-g="all" class="on">全部</button>
  <button data-g="A">A 区</button>
  <button data-g="B">B 区</button>
  <button data-g="C">C 区</button>
  <label>数值下限 <input type="range" id="thr" min="0" max="90" step="5" value="0"></label>
  <label><input type="checkbox" id="on" checked> 启用过滤</label>
  <span id="info">—</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 fromLonLat = ol.proj.fromLonLat;
  var groups = ['A', 'B', 'C'];

  var features = [];
  for (var i = 0; i < 3000; i++) {
    var lon = 115.9 + Math.random() * 1.2;
    var lat = 39.6 + Math.random() * 0.9;
    var f = new ol.Feature({ geometry: new ol.geom.Point(fromLonLat([lon, lat])) });
    f.set('group', groups[i % 3]);
    f.set('value', Math.round(Math.random() * 100));
    features.push(f);
  }

  var source = new ol.source.Vector({ features: features });
  var group = 'all';
  var threshold = 0;
  var enabled = true;

  var colors = { A: 'rgba(31,95,208,0.75)', B: 'rgba(226,110,40,0.75)', C: 'rgba(57,160,168,0.75)' };

  var styleCache = {};
  groups.forEach(function (g) {
    styleCache[g] = new ol.style.Style({
      image: new ol.style.Circle({
        radius: 4,
        fill: new ol.style.Fill({ color: colors[g] }),
        stroke: new ol.style.Stroke({ color: 'rgba(255,255,255,0.8)', width: 1 })
      })
    });
  });

  function styleFn(feature) {
    if (enabled) {
      if (group !== 'all' && feature.get('group') !== group) return null;
      if (feature.get('value') < threshold) return null;
    }
    return styleCache[feature.get('group')];
  }

  var layer = new ol.layer.Vector({ source: source, style: styleFn });

  var map = 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: fromLonLat([116.5, 40.0]), zoom: 11, minZoom: 2, maxZoom: 19 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

  var info = document.getElementById('info');

  function countHit() {
    var n = 0;
    source.getFeatures().forEach(function (f) {
      if (!enabled) { n++; return; }
      if (group !== 'all' && f.get('group') !== group) return;
      if (f.get('value') < threshold) return;
      n++;
    });
    info.textContent = '命中 ' + n + ' / ' + source.getFeatures().length + ' 个点';
  }

  Array.prototype.forEach.call(document.querySelectorAll('.bar button[data-g]'), function (btn) {
    btn.addEventListener('click', function () {
      Array.prototype.forEach.call(document.querySelectorAll('.bar button[data-g]'), function (b) {
        b.classList.remove('on');
      });
      btn.classList.add('on');
      group = btn.getAttribute('data-g');
      layer.changed();
      countHit();
    });
  });

  document.getElementById('thr').addEventListener('input', function () {
    threshold = Number(this.value);
    layer.changed();
    countHit();
  });

  document.getElementById('on').addEventListener('change', function () {
    enabled = this.checked;
    layer.changed();
    countHit();
  });

  countHit();
})();
</script>
</body>
</html>