detect iframe load error

Question

I am loading a user-selected page into an iframe using the src property. If the load fails, I would like to report the problem in terms that will make sense to the user. iframe does not, in general, support onerror according to http://www.w3schools.com/jsref/dom_obj_frame.asp.

The page may come from the user's domain, not mine, so I cannot view the content of the iframe.

I can set a timeout and cancel it from my onload handler if the load is successful, but it would need to be a long timeout to avoid false error reports, and meanwhile Safari on my iPhone has displayed an alert that may confuse the user. Even this does not work for the Kindle Fire browser - it delivers a load event to my handler regardless of whether the load was successful.

Is there any event I can use to detect failure? Is there any way to suppress the default Safari behavior? Any way I can tell whether the load attempt has failed? (If I could do that, I could use a shorter timeout and poll until the load attempt is resolved).

I can require the use of up to date browsers, but would like a solution that is portable among as many smartphones and tablets as possible.

I have tested the AJAX Get idea, and it unfortunately does not work. A cross-domain AJAX Get to an arbitrary URI results in an exception, regardless of whether the target exists and can be loaded into the iframe or not.

Answer 1

You could set your iframe and/or ajax request to always call a page you control (ie: loader.php), sending loader.php the user's requested page via get. From loader.php, use curl or even just file_get_contents to fetch the external page. If the request fails to come back to loader.php, you can check the error there, and return whatever you want your iframe to display.

While my example references the use of php, curl is supported in a variety of scripting languages. It is likely more complicated than other solutions you might have, but would give you access to the response headers as well for troubleshooting why a page load failed.