[筆記] "Unsafe JavaScript attempt to access frame with URL" error with Facebook Javascript API

The following example shows how to create a simple Facebook login button with Facebook javascript API:

Normally, this page would be reloaded if user finished authorized your app. But it won't be reloaded in Chrome due to the follwing error:

Unsafe JavaScript attempt to access frame with URL https://s-static.ak.fbcdn.net/connect/xd_proxy.php?version=3#cb=f363e58d9&origin=http%3A%2F%2Fwww.ab.com%2Ffcb27588&relation=opener&transport=postmessage&frame=fac4c0f18&access_token=AAAEHZBpoK3B0BALv8Cf96gaKEnn4ZBtXgjCOQCFFhVDL4K0rZAE2NGDcqZCPlZByNNKEDmYSGKHQv8jAUM2yGZCHkOcyXUKhoZD&expires_in=0&signed_request=g7sYd_XQx-EBPtQQGk-0ISRMrUDnT4L4WHAmlNsVFBU.eyJhbGdvcml0aG0iOiJITUFDLVNIQTI1NiIsImNvZGUiOiJBUURKYkZBNjZuemduSDBBN0dXWmd2SGxZZkQxQVp4Qm1MSnc0Z3ppUV9FQ25VeEYyZmcyTmJGcFh3UHZDeWhyYnFrT1RxNmRVc2xsb0d4dlFCd290UjRyV0ZsSnJtVjFoNy1QUTlJbTRROXh3MmNKMGU1b0NReWtmT1ZZcXhMUDRVRldVSDgwVU5ic1BLTHdyNk80cFlSVVItQzNIYjhyRWgxek40ZFEzSkpreXhBcU1KSHljcWxETzh2dF96T3ZpN0EiLCJpc3N1ZWRfYXQiOjEzMzExMzg3MjQsInVzZXJfaWQiOiIxMTI5MjgzNDM3In0 from frame with URL http://www.ab.com/login.html. Domains, protocols and ports must match.

Some people use FB.getLoginStatus() to check if user authorized app at page loaded. If page could be reloaded, it's no problem. However, in this case, it's not. 

There are several questions on StackOverflow related to this:

http://stackoverflow.com/questions/3577947/facebook-gives-unsafe-javascript-attempt-to-access-frame-with-url-error-in-chr

http://stackoverflow.com/questions/8013008/facebook-authentication-unsafe-javascript-attempt-to-access-frame-with-url

http://stackoverflow.com/questions/3010170/unsafe-javascript-attempt-to-access-frame-with-url-error-being-continuously

But none of these solves my problem. I don't want to solve this with introduce PHP sdk. I would like to solve it with pure front end codes. 

Therefore, I find 3 solutions:

1. Ignore the error and register login event to solve the problem:
2. Add attribute "show-faces="true"" to <fb:login-button> to solve
3. Add attribute "render-in-iframe="true"" to <fb:login-button> to solve. This is a bad idea since this is an undocumented attribute.

In solution 2 and 3, login-button seems to be placed into an iframe. And 3 would display an incomplete login button (bug?)