How to obtain the error message in XDomainRequest object?

Question

I see my method for error handling invoked but since there's no arguments in, I don't know how to check what kind of error it is.

var xdr = new XDomainRequest();
xdr.onerror = function(e){
  alert(e);
}

In the above example e is undefined.

Answer 1

When executing CORS, the error message is not available. And XDomainRequest is by the very definition of it cross-origin.

See this discussion as well as this definition.