"Access is denied" JavaScript error when trying to access the document object of a programmatically-created <iframe> (IE-only)
I have project in which I need to create an <iframe> element using JavaScript and append it to the DOM. After that, I need to insert some content into the <iframe>. It's a widget that will be embedded in third-party websites.
I don't set the "src" attribute of the <iframe> since I don't want to load a page; rather, it is used to isolate/sandbox the content that I insert into it so that I don't run into CSS or JavaScript conflicts with the parent page. I'm using JSONP to load some HTML content from a server and insert it in this <iframe>.
I have this working fine, with one serious exception - if the document.domain property is set in the parent page (which it may be in certain environments in which this widget is deployed), Internet Explorer (probably all versions, but I've confirmed in 6, 7, and 8) gives me an "Access is denied" error when I try to access the document object of this <iframe> I've created. It doesn't happen in any other browsers I've tested in (all major modern ones).
This makes some sense, since I'm aware that Internet Explorer requires you to set the document.domain of all windows/frames that will communicate with each other to the same value. However, I'm not aware of any way to set this value on a document that I can't access.
Is anyone aware of a way to do this - somehow set the document.domain property of this dynamically created <iframe>? Or am I not looking at it from the right angle - is there another way to achieve what I'm going for without running into this problem? I do need to use an <iframe> in any case, as the isolated/sandboxed window is crucial to the functionality of this widget.
Here's my test code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title>Document.domain Test</title>
<script type="text/javascript">
document.domain = 'onespot.com'; // set the page's document.domain
</script>
</head>
<body>
<p>This is a paragraph above the <iframe>.</p>
<div id="placeholder"></div>
<p>This is a paragraph below the <iframe>.</p>
<script type="text/javascript">
var iframe = document.createElement('iframe'), doc; // create <iframe> element
document.getElementById('placeholder').appendChild(iframe); // append <iframe> element to the placeholder element
setTimeout(function() { // set a timeout to give browsers a chance to recognize the <iframe>
doc = iframe.contentWindow || iframe.contentDocument; // get a handle on the <iframe> document
alert(doc);
if (doc.document) { // HEREIN LIES THE PROBLEM
doc = doc.document;
}
doc.body.innerHTML = '<h1>Hello!</h1>'; // add an element
}, 10);
</script>
</body>
</html>
I've hosted it at:
http://troy.onespot.com/static/access_denied.html
As you'll see if you load this page in IE, at the point that I call alert(), I do have a handle on the window object of the <iframe>; I just can't get any deeper, into its document object.
Thanks very much for any help or suggestions! I'll be indebted to whomever can help me find a solution to this.
Solution 1:
if the document.domain property is set in the parent page, Internet Explorer gives me an "Access is denied"
Sigh. Yeah, it's an IE issue (bug? difficult to say as there is no documented standard for this kind of unpleasantness). When you create a srcless iframe it receives a document.domain from the parent document's location.host instead of its document.domain. At that point you've pretty much lost as you can't change it.
A horrendous workaround is to set src to a javascript: URL (urgh!):
iframe.src= "javascript:'<html><body><p>Hello<\/p><script>do things;<\/script>'";
But for some reason, such a document is unable to set its own document.domain from script in IE (good old “unspecified error”), so you can't use that to regain a bridge between the parent(*). You could use it to write the whole document HTML, assuming the widget doesn't need to talk to its parent document once it's instantiated.
However iframe JavaScript URLs don't work in Safari, so you'd still need some kind of browser-sniffing to choose which method to use.
*: For some other reason, you can, in IE, set document.domain from a second document, document.written by the first document. So this works:
if (isIE)
iframe.src= "javascript:'<script>window.onload=function(){document.write(\\'<script>document.domain=\\\""+document.domain+"\\\";<\\\\/script>\\');document.close();};<\/script>'";
At this point the hideousness level is too high for me, I'm out. I'd do the external HTML like David said.
Solution 2:
Well yes, the access exception is due to the fact that document.domain must match in your parent and your iframe, and before they do, you won't be able to programmatically set the document.domain property of your iframe.
I think your best option here is to point the page to a template of your own:
iframe.src = '/myiframe.htm#' + document.domain;
And in myiframe.htm:
document.domain = location.hash.substring(1);
Solution 3:
well i actually have a very similar problem, but with a twist... say the top level site is a.foo.com - now i set document domain to a.foo.com
then in the iframe that i create / own,i also set it too a.foo.com
note that i cant set them too foo.com b/c there is another iframe in the page pointed to b.a.foo.com (which again uses a.foo.com but i cant change the script code there)
youll note that im essentially setting document.domain to what it already would be anyway...but i have to do that to access the other iframe i mentioned from b.a.foo.com
inside my frame, after i set the domain, eventhough all iframes have the same setting, i still get an error when reaching up into the parent in IE 6/7
there are other things that r really bizaree
in the outside / top level, if i wait for its onload event, and set a timer, eventually i can reach down into the frame i need to access....but i can never reach from bottom up... and i really need to be able to
also if i set everything to be foo.com (which as i said i cannot do) IT WORKS! but for some reason, when using the same value as location.host....it doesnt and its freaking killing me.....
Solution 4:
I just use <iframe src="about:blank" ...></iframe> and it works fine.
Solution 5:
for IE, the port matters. In between domains, it should be same port.