This article gives a pretty good explanation:
http://www.ibm.com/developerworks/library/wa-aj-jsonp1/
The gist is that XMLHttpRequest is limited to same-domain urls.
However there is a workaround for JSON (they call it JSONP) that uses
the ability to load javascript dynamically from another domain.
Essentially, it seems you can bypass the cross-domain restriction by
this trick:
var script = document.createElement('script');
script.setAttribute('src', url);
Apparently in this instance url doesn't have to be a url on the same domain.
I don't see why this couldn't be used to insert any sort of data at all,
but it does rely on javascript.
-Mike
On 12/08/2010 08:08 AM, Elliotte Rusty Harold wrote:
> On Tue, Dec 7, 2010 at 7:15 PM, Rob Koberg<> wrote:
>
>
>> First thing: Get the browser builders to allow cross domain loading of
>> XML. Without that you might as just bang your head on a post. (even
>> with that, you will just be banging your head on a padded post)
>>
> Just want to double check this. JSON can be loaded cross-domain and
> XML can't, right? I.e. I can eval JSON from an arbitrary host in my
> browser-based JavaScript and I can't load XML using XmlHTTPRequest
> unless it comes from the same host? Or is it more subtle than that? If
> so, is there a detailed analysis somewhere of exactly under what
> conditions I can load JSON from where and how?
>
> Googling around I see some blog posts, but no detailed analysis.
>
>
