jQuery cross domain request response headers

Question

I am making cross domain ajax requests with html data type. They work OK as I include

Access-Control-Allow-Origin

in the response from the server. Problem is I need to get certain headers from the server's response and whatever I do, response headers apart from "content type" return null.

jQuery does the request, retrieves the response including headers (I can see it from the traffic) but it doesn't parse it.

I have tried using

crossDomain: true

It didn't help. Here is the sample response from the server.

Access-Control-Allow-Origin:*
Cache-Control:private
Content-Encoding:gzip
Content-Length:514
Content-Type:text/html; charset=utf-8 
X-MYRESPONSEHEADER:1

If requesting and responding document are on same server

 success: function (data, status, xhr) {
        totalRows = xhr.getResponseHeader("X-MYRESPONSEHEADER");

works fine. I have also tried to assign $.ajax to a variable like

var jQxhr = $.ajax(.....

I don't see why it wouldn't be parsed since jQuery actually makes the request and gets the response

Any ideas? Am I missing something?

Update or dragon's comment

Headers sent to request

HTTP/1.1 200 OK
Cache-Control: private
Content-Type: text/html; charset=utf-8
Content-Encoding: gzip
Vary: Accept-Encoding
Server: Microsoft-IIS/7.5
Access-Control-Allow-Origin: *
Access-Control-Allow-Headers: X-MYRESPONSEHEADER
Access-Control-Allow-Methods: POST
Access-Control-Allow-Methods: GET
X-MYRESPONSEHEADER: 24
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Wed, 29 Feb 2012 11:34:21 GMT

Content-Length: 514

Answer 1

You need to add another CORS-specific header in the server response, Access-Control-Allow-Headers. In this case,

Access-Control-Allow-Headers: X-MYRESPONSEHEADER

Ref: https://developer.mozilla.org/en/http_access_control#Access-Control-Allow-Headers

Answer 2

If you're using aws s3 (and I assume this is applicable otherwise), the problem is possibly a missing CORS configuration tag. I ran in to a similar problem with missing. Here's my completed configuration:

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
    <CORSRule>
        <AllowedOrigin>http://localhost:3000</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <AllowedMethod>POST</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>*</AllowedHeader>
        <ExposeHeader>*</ExposeHeader>
    </CORSRule>
</CORSConfiguration>

AllowedHeader sets the Access-Control-Request-Headers header, and ExposeHeader sets Access-Control-Expose-Headers header, without which the browser wont allow javascript to use the returned headers.

Answer 3

To read headers other than content-type in the server's response, the server must supply Access-Control-Expose-Headers, eg:

Access-Control-Expose-Headers: X-MYRESPONSEHEADER 

@dragon's answer mentionsAccess-Control-Allow-Headers which only controls which headers the client can send when making a request to the server.

Useful CORS tutorial here: http://www.html5rocks.com/en/tutorials/cors/