<div id="map"></div>
<input type="hidden" id="mapSubmit" />
<script>
  var map;
  function initMap() {
    // instantiator GreenValleyMap(mapDiv, hiddenField, params)
    map = new GreenValleyMap(document.getElementById('map'),document.getElementById('mapSubmit'),{
      "center": {"lat":50.965698,"lng":5.502443},
      "zoom": 8,
      "maxtags": 3,
      "search": true,
      "layers":[
        GRB: "http://geoservices.informatievlaanderen.be/raadpleegdiensten/GRB-basiskaart/wms?request=GetCapabilities&service=WMS",
        GRBGrijs:"http://geoservices.informatievlaanderen.be/raadpleegdiensten/GRB-basiskaart-grijs/wms?request=GetCapabilities&service=WMS"
      ]
    });
  }
</script>