Zoom Slider

<!--
  示例：缩放滑块控件
  要点：自定义 Control 内含 range 输入，setZoom 与 change:resolution 双向同步
  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>缩放滑块控件</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;
       font-size:12px;color:#58606e}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
  .zoom-ctl{top:.5em;left:.5em;background:#fff;padding:6px 10px;border-radius:4px;
            box-shadow:0 1px 4px rgba(0,0,0,.2)}
  .zoom-ctl input{width:120px;vertical-align:middle}
  .zoom-ctl span{font-size:11px;color:#58606e;margin-left:6px}
</style>
</head>
<body>
<div class="bar">
  <span id="info">zoom —</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;
  }

  class ZoomSlider extends ol.control.Control {
    constructor() {
      var el = document.createElement('div');
      el.className = 'ol-control zoom-ctl';

      var input = document.createElement('input');
      input.type = 'range';
      input.min = 3;
      input.max = 18;
      input.step = 0.5;
      input.value = 12;
      input.setAttribute('aria-label', '地图层级');
      el.appendChild(input);

      super({ element: el });
      this.input_ = input;

      var self = this;
      input.addEventListener('input', function () {
        var map = self.getMap();
        if (map) {
          map.getView().setZoom(Number(input.value));
        }
      });
    }

    sync(zoom) {
      this.input_.value = zoom;
    }
  }

  var slider = new ZoomSlider();

  var view = new ol.View({
    center: ol.proj.fromLonLat([116.3974, 39.9093]),
    zoom: 12,
    minZoom: 3,
    maxZoom: 18
  });

  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'}) })],
    view: view,
    controls: ol.control.defaults.defaults({ attribution: false }).extend([slider]),
    interactions: ol.interaction.defaults.defaults({ doubleClickZoom: false })
  });

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

  view.on('change:resolution', function () {
    var z = view.getZoom();
    slider.sync(z);
    info.textContent = 'zoom ' + z.toFixed(1);
  });
})();
</script>
</body>
</html>