OPENLAYERS 6如何获取多个kml文件的界限

import 'ol/ol.css';
import Map from 'ol/Map';
import View from 'ol/View';
import VectorSource from 'ol/source/Vector';
import VectorLayer from 'ol/layer/Vector';
import { Style, Stroke } from 'ol/style';
import { get as getProjection } from 'ol/proj';
import { parseKML } from 'ol/format/KML';

// 创建地图实例
const map = new Map({
  target: 'map',
  layers: [
    new TileLayer({
      source: new XYZ({
        url: 'https://{a-c}.tile.openstreetmap.org/{z}/{x}/{y}.png'
      })
    })
  ],
  view: new View({
    center: [0, 0],
    zoom: 2
  })
});

// 加载 KML 文件并获取边界
function loadKMLAndGetBounds(url) {
  return fetch(url)
    .then(response => response.text())
    .then(text => {
      const format = new KML();
      const features = format.readFeatures(text);
      let bounds = null;
      features.forEach(feature => {
        const featureBounds = feature.getGeometry().getBounds();
        if (!bounds) {
          bounds = featureBounds;
        } else {
          bounds = bounds.extend(featureBounds);
        }
      });
      return bounds;
    });
}

// 假设有两个 KML 文件的 URL
const kmlUrls = ['url_to_kml_file1.kml', 'url_to_kml_file2.kml'];

// 获取所有 KML 文件的边界并合并
Promise.all(kmlUrls.map(loadKMLAndGetBounds))
  .then(boundsArray => {
    let mergedBounds = null;
    boundsArray.forEach(bounds => {
      if (!mergedBounds) {
        mergedBounds = bounds;
      } else {
        mergedBounds = mergedBounds.extend(bounds);
      }
    });
    console.log('Merged Bounds:', mergedBounds);
    // 可以将合并后的边界显示在地图上
    if (mergedBounds) {
      map.getView().fit(mergedBounds, map.getSize());
    }
  })
  .catch(error => {
    console.error('Error loading KML files:', error);
  });