SmartGWT TileGrid Default Tile Image

(Using most recent version of SmartGWT)

I am creating a TileGrid to display images + textin SmartGWT; this is up and running.

To set the image I am doing:

node.setAttribute("picture", "http://servername/images/3334445000.jpg");

With this, the url will change based on a number associated with each 'node' (unique identifier). The desired functionality is to have the "picture" attribute set to a default image if the specific image doesn't exist.

For example:

if( "http://servername/images/3334445000.jpg" [exists] )
    node.setAttr开发者_如何转开发ibute("picture", "http://servername/images/3334445000.jpg");
else
   node.setAttribute("picture", "http://servername/images/default.jpg");

The [exists] portion being what I am having troubles with. I'm sure there is an easy way to make this happen, but I'm new to SmartGWT and still learning. Again, everything else is working, no errors; just need guidance on the default image.