Troubleshooting

Some people reported that it doesn't work in IExplorer 8/9. After doing some more testing I quickly came to the conclusion that this is because XDomainRequest simply sucks the life out of you with (1) too many restrictions + (2) no way of debugging whatever happened.

Here's the MSDN page describing current issues with XDomainRequest:

XDomainRequest Restrictions, Limitations and Workarounds

Summarized in the context of our use-case, when doing requests using this utility / debugging / testing it, do the following:

• IExplorer does not accept a wildcard for Access-Control-Allow-Origin
• related to the item above, IExplorer sometimes is configured (or is blocked by a firewall) to NOT send the HTTP Referer. So do NOT base your server-side implementation on it to emulate wildcards
• do not try to send custom headers, IExplorer will ignore them ... so NO
• do not try to send cookies, IExplorer will strip them out and sending cookies is problematic in GENERAL, unless withCredentials is involved
• withCredentials is not supported by IExplorer and it is weird anyway - pass everything needed to the server using www-urlencoded requests and set cookies on the client with your own Javascript code, based on whatever comes from the response's body
• fresh installs of IExplorer 6 and 7 do not have Flash 9 installed, so flXHR will not work
• in IExplorer 8 (at least originally, I don't know if it wasn't updated), the only Content-Type supported for your request is text/plain. This means the server may not receive a Content-Type: www-urlencoded header in the request and may assume it must not parse it, so do tests and be prepared to parse the request yourself. So do not rely on multipart/form-data to work either. Yes I know, this sucks.