I have hit a wall with this issue. I guess it is some kind of IE bug but I want to be sure.

So the question is. Why does IE10 XmlHttpRequest.status returns 0 instead of 401?

var xmlhttp=new XMLHttpRequest();



xmlhttp.onreadystatechange=function()

  {

  if (xmlhttp.readyState==4)

    {

      document.getElementById(rescode).innerHTML=Request completed with status: +xmlhttp.status;

    }

  }

xmlhttp.open(GET,http://hosting.gregy.cz/cors/,true);

xmlhttp.send();

See plunker here: http://plnkr.co/edit/E2lCflPDHHaQi7t79IeM?p=preview

This code fires a CORS request which always returns 401. Firefox and chrome correctly return 401 in status attribute but IE10 returns 0. This issue breaks authentication handling methods I use for my project.

Thank you

Edit:

I have modified the plunker with onload and onerror event handlers (tip from monsur's comment), but the result is still the same.

I have also made sure IE10 has no compatibility mode selected. (tip from cernunnos's comment)