Using Javascript reflection to get obfuscated Google Map object members

If you’ve had much to do with Google Maps, then you’ve probably come across the GMarker object. You use it when making your own custom markers on a Google Map.

var stdIcon.image = "/images/myMarker.png";
stdIcon.iconSize = new GSize(20, 20);
stdIcon.iconAnchor = new GPoint(16, 16);
stdIcon.infoWindowAnchor = new GPoint(25, 7);   
var  marker = new GMarker(point, {icon:stdIcon});
map.addOverlay(marker);

Once the marker’s been created and placed on the map, then there didn’t seem to be anyway to get the image element of the marker so I could do some funky stuff with it.

So, I opened up FireBug and had a look at the GMarkers internals:

The property I had been looking for was cleverly obfuscated with the boring name of Mj. “Aha!” I thought, “Gotcha Google! Can’t hide it away from me!” and proceeded to write code that referenced this highly secretive Mj property.

A month went by though, and I noticed that my code no longer worked – the Mj property had been renamed to Zj, breaking all my code! Teach me for referencing an Obfuscated property I guess.

So, I got around it using Javascript reflection.

function getMarkerImage(marker) {
  for (var memberName in marker) {
    var memberObj = marker[memberName];
    if ((memberObj) && (memberObj.tagName == "IMG") {
      return memberObj;            
    }
  }
}

This method finds the first property of the GMarker class that has a tagName == “IMG”.