We have some user images on a server (let's call it 'a') at work and I wanted to automatically inline them on another page on another server (which, for demonstration purposes we shall call 'b') if they exist. This, I felt, was a job for this AJAX malarkey that I'd heard so much about.
This
<html>
<head>
<script type="text/javascript">
function picture(name)
{
var xmlhttp=false;
/*@cc_on @*/
/*@if (@_jscript_version >= 5)
// JScript gives us Conditional compilation
// so we can cope with old IE versions.
// and security blocked creation of the objects.
try {
xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
} catch (E) {
xmlhttp = false;
}
}
@end @*/
if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
xmlhttp = new XMLHttpRequest();
}
var url = "http://a/"+name+".jpg";
xmlhttp.open("HEAD", url,true);
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4) {
if (xmlhttp.status==200) {
document.write("<img src='"+url+"'>");
}
}
}
xmlhttp.send(null);
}
</script>
</head>
<body>
<div>
<script type="text/javascript">
picture('foobar')
</script>
</div>
<div>
<script type="text/javascript">
picture('doesnt exist')
</script>
</div>
</body>
</html>
didn't work, throwing up errors like
"uncaught exception: Permission denied to call method XMLHTTRequest.open"
To get round the security thing I had to stick a script on b
#!/usr/bin/perl -w
use strict;
use CGI;
use LWP::Simple;
$|++;
my $q = CGI->new;
my $n = $q->param('url');
my $u = "http://a/${n}.jpg";
if (head($u)) {
print $q->header('text/html');
} else {
print $q->header('text/html', '404 Not Found');
}
print "\n";
exit 0;
And change the line in the javascript to be
xmlhttp.open("HEAD", "/proxy_check?url="+url,true);
And lo! It worked. Huzzah!
