How to switch back from ImageMapType to normal map

I am not sure how to switch back from ImageMapType to normal map. The problem is described in code as followings (pseudo code):

    var myMap;
    var curLabLocation = new google.maps.LatLng(36.415793, -121.084421);
    var mapOptions = {
      zoom: 21,
      streetViewControl: false,
      center: curLabLocation,
      mapTypeId: google.maps.MapTypeId.MAP
    };
    var $map = $('#map-canvas');

    myMap = new google.maps.Map($map[0], mapOptions);


    // A) Switch to image type map. NO problem
    var imageMapType = new google.maps.ImageMapType({
      getTileUrl: function(coord, zoom) {
          // Simply empty. How to delete this????? After B)
          // this function still working, which prevent
          // normal map to show up.
          return null;
      },
      tileSize: new google.maps.Size(256, 256),

      maxZoom: 23,
      minZoom: 22,
      name: 'image type map'
    });


    myMap.mapTypes.set('imagetypemap', imageMapType);
    myMap.setMapTypeId('imagetypemap');

   // Now, it works fine with ImageMapType.


   // B) Switch back to normal map. Problem is the map is empty due
   // to getTileUrl: function(coord, zoom) {} still working.
   myMap.setMapTypeId(google.maps.MapTypeId.MAP);

   // I tried this. But not working. myMap.overlayMapTypes.length=0   before clear() is called. So, this is not right way to clear ImageMapType.

   myMap.overlayMapTypes.clear();
   myMap.setMapTypeId(google.maps.MapTypeId.MAP);

Do I need to re-create the map object? Is there way not to re-create the map object? If no, how to do it?

Copyright Notice：Content Author:「user3792705」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/33158449/how-to-switch-back-from-imagemaptype-to-normal-map