Getting JavaScript exception happening in iframe surface

Question

Here is the situation:

• A page (iframe.html) has an iframe loading another page (iframe-content.html).
• An JavaScript error might happen when iframe-content.html is loaded in the iframe.
• I'd like that exception to be visible to the browser (e.g. shown in Firefox error console, or Firebug).

Here is what I see:

1. When iframe.html is initially loaded, and loads iframe-content.html with src="iframe-content.html", the JavaScript exception shows in Firebug.
2. However, if the page is loaded in JavaScript (document.getElementById('iframe').src = 'iframe-content.html'), the exception doesn't show.

You can reproduce this by going to:

1. http://avernet.googlepages.com/iframe.html with Firefox.
2. You'll see the exception as iframe-content.html is loaded.
3. Click on the button: the content of the iframe is loaded again, but this time the exception doesn't show in Firebug.

Is there a way at #3 to have the exception show, instead of it being silently ignored? (You can't use a try/catch around the JS code that sets the src, as this code returns immediately before the page is loaded in the iframe.)

Answer 1

It seems that your iframe page is not really loaded on the second time. Or it's loaded from the cache and the error is ignored. This is interesting, but I think I found an way around it.

function setContent() {
    try {
        console.log("Loading iframe content");
        document.getElementById('iframe').src = 'iframe-content.html?foo=bar';
    } catch (e) {
        console.log("Caught", e);
    }
    console.log("Done loading");
}

With that the error should appear.

What I did, was to trick the browser to think that I'm loading a brand new page as the parameters after the url have changed.

'iframe-content.html?foo=bar';

You could replace my "bar" string with a changing timestamp. Sure, it would avoid the cache, but it would also force it to generate the error like you wished.

Answer 2

I have noticed that when i use noscript the iframe get blocked (it can be unblocked). Is it possible for an iframe not to be blocked? This isnt for 'naughty' reasons. Just made a site and the customer wasnt happy that their machine didnt display it (due to 'noscript' being installed).

Thanks in advance.

lien