Right up until MS changed their implementation, say to version 7. MSIE's implementation of XHR exposed internal details of the ActiveX-based implementation whic

Right up until MS changed their implementation, say to version 7. MSIE's implementation of XHR exposed internal details of the ActiveX-based implementation which were subject to change-- it was never meant to be an external API, but rather, to enable features in Outlook Web Access. Thus, any third-party implementation would have to involve making a list of special magic strings to recognize in the ActiveXObject() call, then delegate to code that attempts to replicate internal implementation details of the given ActiveX object.