检查图像是否存在

I use the following code to refresh an image in the browser. I just want to modify the code in order to first check if the image exists and then display the image. If the image does not exist I will only refresh the image to the previous version of the picture. Can someone point me how to accomplish this using javascript or jquery?

<html>
    <head>
        <script language="JavaScript">
            function refreshIt(element) {
                setTimeout(function() {
                    element.src = element.src.split('?')[0] + '?' + new Date().getTime();
                    refreshIt(element);
                }, 500); // refresh every 500ms
            }
        </script>
    </head>
    <body>
        <img src="swt.png" name="myCam" onload="refreshIt(this)">
    </body>
</html>

Edited: I need a combination of the already implemented functionality plus the file checking.

Functionality:

if image exist 
  refresh image
else 
  show cached image

Something like this:

$('#image_id').error(function() {
  alert('Image does not exist !!');
});