Why doesn't dojo.io.script.get() execute the provided error function when receiving a 404? - dojo

Question

I am trying to use the following to do a cross-domain get:
dojo.io.script.get({
url: myUrl,
callbackParamName: "callback",
preventCache: true,
load: dojo.hitch( this, loadFunction ),
error: dojo.hitch( this, function() {
console.log('Error!!!');
})
});
The load function runs fine, however, when the server returns a 404, the error function does not run. Can anyone tell me why?
EDIT
After some investigation, I found that a timeout and handler could be implemented in the following way:
dojo.io.script.get({
url: myUrl,
callbackParamName: "callback",
timeout: 2000
}).then(function(data){
console.log(data);
}, function(error){
alert(error);
});
This uses functionality provided by the dojo.Deferred object.

Answer 1

When accessing server with script tags (that what dojo.io.script.get does), status code and headers are not available.
You may try some other ways to detect a problem, like using a timeout and analyzing a content of a script. The latter is problematic for JSONP calls (like in your example).

Answer 2

I realize this is old but I thought I'd share a solution in case others, like I had, come across this thread.
dojo.io.script is essentially adding a <script/> to your html page. So you can try this:
var script = document.createElement('script');
script.setAttribute('type', 'text/javascript');
script.setAttribute('src', myUrl);
script.onerror = function() {
debugger
}
script.onload = function() {
debugger
}
document.getElementsByTagName('body')[0].appendChild(script);
That way if the script fails to load the onerror event is called.
*This may not work in every instance but is a good start