maptalks - Geometry转化为GeoJSON

Geometry转化为GeoJSON
index.html
<!DOCTYPE html>
<html>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>JSON序列化 - Geometry转化为GeoJSON</title>
  <style type="text/css">
    html,body{margin:0px;height:100%;width:100%}
    .container{float:left;width:100%;height:100%}
    #info{position:fixed;background-color:rgba(13, 13, 13, 0.5);padding:10px 10px 10px 10px;font:13px bold sans-serif;color:#fff;left:0px;top:0px;width:100%;height:70px;overflow:hidden}
  </style>
  <link rel="stylesheet" href="https://unpkg.com/maptalks/dist/maptalks.css">
  <script type="text/javascript" src="https://unpkg.com/maptalks/dist/maptalks.min.js"></script>
  <body>

    <div id="map" class="container"></div>
    <div id="info">

    </div>

    <script>
      var map = new maptalks.Map('map', {
        center: [-0.113049,51.498568],
        zoom: 14,
        baseLayer: new maptalks.TileLayer('base', {
          urlTemplate: 'https://{s}.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png',
          subdomains: ['a','b','c','d'],
          attribution: '&copy; <a href="http://osm.org">OpenStreetMap</a> contributors, &copy; <a href="https://carto.com/">CARTO</a>'
        }),
        layers : [
          new maptalks.VectorLayer('v')
        ]
      });

      var marker = new maptalks.Marker([-0.113049,51.498568], {
        'properties': {
          'name': 'point marker'
        }
      }).addTo(map.getLayer('v'));

      document.getElementById('info').innerHTML = JSON.stringify(marker.toGeoJSON());

    </script>
  </body>
</html>