如何使Google地图标记每5秒刷新一次，而无需重新加载整个地图

Question

在过去的两个小时中，我一直试图仅重新加载标记，但我只能重新加载整个地图

我曾尝试将一些bindmarkers功能放进去，但仍然无济于事

    function initMap() {
    var map = new google.maps.Map(document.getElementById('map'), {
      center: new google.maps.LatLng(17.1899, -88.534721),
      zoom: 8
    });
    var infoWindow = new google.maps.InfoWindow;

      // Change this depending on the name of your PHP or XML file

      downloadUrl('xml1.php', function(data) {
        var xml = data.responseXML;
        var markers = xml.documentElement.getElementsByTagName('marker');
        Array.prototype.forEach.call(markers, function(markerElem) {
          var id = markerElem.getAttribute('id');
          var name = markerElem.getAttribute('name');
          var address = markerElem.getAttribute('address');
          var type = markerElem.getAttribute('type');
          var point = new google.maps.LatLng(
              parseFloat(markerElem.getAttribute('lat')),
              parseFloat(markerElem.getAttribute('lng')));

          var infowincontent = document.createElement('div');
          var strong = document.createElement('strong');
          strong.textContent = name
          infowincontent.appendChild(strong);
          infowincontent.appendChild(document.createElement('br'));

          var text = document.createElement('text');
          text.textContent = id
          infowincontent.appendChild(text);
          var icon = customLabel[id] || {};
          var marker = new google.maps.Marker({
            map: map,
            position: point,
            label: icon.label
          });
          marker.addListener('click', function() {
            infoWindow.setContent(infowincontent);
            infoWindow.open(map, marker);
          });
        });
      });
    }