کد کامل:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
    <html>
    <head>
    <title>Using AJAX to check if a file exists</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8"></meta>
    <script type="text/javascript">
    var req, image, warning, imagepath;
     
    function d(o)
    {
    return document.getElementById(o);
    }
     
    function loadimage(_imagepath)
    {
    image = d("image");
    image.style.display = "none";
     
    imagepath = _imagepath;
     
    warning = d("warning");
    warning.innerHTML = "Loading ...";
     
    req = getreq();
    req.onreadystatechange = imagexists;
    req.open("get", imagepath, true);
    req.send(null);
    }
     
    function imagexists()
    {
    if(req.readyState == 4)
    {
    if(req.status == 200)
    {
    warning.innerHTML = "Image exists";
    image.style.display = "block";
    image.src = imagepath;
    }
    else
    {
    warning.innerHTML = "Image does not exist";
    image.style.display = "none";
    }
    }
    }
     
    function getreq()
    {
    if(window.XMLHttpRequest)
    return new XMLHttpRequest();
    else if(window.ActiveXObject)
    return new ActiveXObject("Microsoft.XMLHTTP");
    }
     
    </script>
    <style type="text/css">
    * { font-family: Verdana, Arial, sans-serif; }
    body { background-color: #FFF; }
    h1 { font-size: 14px; }
    #warning { margin: 10px; }
    #img { border: 1px solid #CCC; padding: 3px; margin: 10px; }
    </style>
    </head>
     
    <body>
     
    <h1>Check an image exists with AJAX</h1>
     
    <input type="button" value="Load real image" onclick="loadimage('IMAG0272.jpg');" />
    <input type="button" value="Load fake image" onclick="loadimage('5hhhh_thumb.jpg');" />
     
    <div id="warning"></div>
    <img id="image" src="blank.jpg" style="display: none;" alt="" />
     
    </body>
    </html>