Object.create fails for IE<9 if document.domain is set

[angus-c]

If the main document has domain attribute set then we get a permission denied error trying to access iframe.contentWindow.Object (due to same-domain restriction)

Tried to patch it up with very hokey iframe.src code:

iframe.src = "javascript:'<script>window.onload=function(){document.write(\\'<script>document.domain=\\\"" + document.domain + "\\\";<\\\\/script>\\');document.close();};<\/script>'";

but it didn't do the trick.

This issue is preventing twitter.com from upgrading to latest es5-shim

[kriskowal]

The use of the iframe is a recent addition. We may be able to back it out. Thanks.

[ghost]

Relevent StackOverflow thread: http://stackoverflow.com/questions/1886547/access-is-denied-javascript-error-when-trying-to-access-the-document-object-of?rq=1

[kriskowal]

Looks like we can’t back it out. This is our only recourse for getting Object.create(null) to work on IE.

@angus-c, one issue I see with the solution you tried is that there is a chance that the onload handler is introducing a race between the iframe loading and the first use of Object.create. Does the domain need to be assigned after the load event?

[angus-c]

The code is currently in an IIFE - so gets invoked even if Object.create(null)
not used. Could make it contingent on Object.create(null) so doesn't break
in loading. I think Brandon mentioned this

Yes agree about the sync issue.

On Wed, Feb 6, 2013 at 12:47 PM, Kris Kowal notifications@github.comwrote:

Looks like we can’t back it out. This is our only recourse for getting
Object.create(null) to work on IE.

@angus-c https://github.com/angus-c, one issue I see with the solution
you tried is that there is a chance that the onload handler is introducing
a race between the iframe loading and the first use of Object.create. Does
the domain need to be assigned after the load event?

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/150#issuecomment-13204211.

[kriskowal]

Okay. Let’s set up the iframe on the first use.

[kriskowal]

@angus-c, can you check out the pull request I just posted and let me know if that resolves the issue for you?

[ghost]

Actually, I believe new ActiveXObject("htmlfile") is a viable alternative to a frame in IE (though it needs to be cached so that it's not garbage collected; the cache can be cleared via cache.length = 0 on unload).

We used something like this in FuseJS:

// `cache` and the listener only need to be set up once.
var cache = [];
if (typeof attachEvent != "undefined") {
  attachEvent("onunload", function() {
    cache.length = 0;
});
// ...
var doc = new ActiveXObject("htmlfile");
doc.write("<script><\/script>");
doc.close();
cache.push(doc);
var empty = doc.parentWindow.Object.prototype;
// ...

[ghost]

FuseJS is exactly who I was thinking of earlier: "I know people have used hidden iframes or SOMETHING for shims in old IE and been successful". I think that is likely to be the winner, as I have a feeling the above delayed-loading solution doesn't address the underlying problem (haven't tested it though).

[kriskowal]

@kitcambridge, go for it!

[ghost]

Working on a branch now—we'll probably want to keep the frame around for cases where the browser doesn't support __proto__ or ActiveX (i.e., older versions of Opera), or ActiveX is disabled.

[angus-c]

Still failing in same place - not sure why, given your change - hard to
debug minified code.
In any case @kit's fix looks promising - as it would actually support
Object.create(null)

On Wed, Feb 6, 2013 at 1:08 PM, Kris Kowal notifications@github.com wrote:

@angus-c https://github.com/angus-c, can you check out the pull request
I just posted and let me know if that resolves the issue for you?

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/150#issuecomment-13205207.

[jdalton]

Yap, as Kit pointed out we used, in part, iframes and ActiveX for "Sandboxed Natives". The ActiveX('htmlfile') avoids issues with HTTPS mixed content warnings in IE6 and document.domain issues in older IE. Notice that we clear the cache on window unload, that's because there is a memory-leak associated with ActiveX('htmlfile') and that helped avoid it.

[jdalton]

Here is notes from an old WIP rewrite of Sandboxed Natives (I should really revisit that):

// The htmlfile ActiveX object is supported by IE4+ and avoids https mixed
// content warnings in IE6. It's also used to workaround access denied errors
// thrown when using iframes to create sandboxes after the `document.domain` is
// set (Opera 9.25 is out of luck here).
!isHostType( window, 'XMLHttpRequest' ) && window.location == 'https:' && has.activex ||
// iframes are the fastest and prefered technique
has.iframe ||
// optimized Node.js support
has.nodejs ||
// A fallback for non browser environments supported by JavaScript engines
// such as Carakan, JaegerMonkey, JavaScriptCore, KJS, Nitro, Rhino,
// SpiderMonkey, SquirrelFish (Extreme), Tamarin, TraceMonkey, and V8.
has.proto;

[ryanve]

Another possible way to quasi-emulate Object.create(null) would be to convert a plain object into an emptyParent by setting all its properties/dontEnums to undefined (such that they override Object.prototype properties without modifying them). Then Object.create(null) could do Object.create(emptyParent). It's not exactly the same, but for most uses, it would suffice.