jQuery Ajax access custom response headers

Question

I'm using some API, and I noticed that in the response I have this:

I'd need to read the "x-dl-units-left", but I get null:

$.ajax(ajaxConfig).done(function(response, textStatus, xhr){
  var left = xhr.getResponseHeader("x-dl-units-left"); //null
  var all = xhr.getAllResponseHeaders(); // "content-type: application/json;charset=UTF-8"
});

Anyone who might know why?? :(

Thank you

Watchmaker

Thx 4 the edit Rory :) I forgot to press Ctrl+K :D – Watchmaker

This answer seems to explain the problem quite well. – Lulualaba

Answer 1

The issue is because the request is using CORS. Therefore you need to explicitly allow your custom headers to be exposed to the recipient. To do this add a Access-Control-Expose-Headers header to the response, eg:

Access-Control-Expose-Headers: x-dl-units-left, x-dl-units, [other headers as needed...]

Note that this must be done on the server that creates the response. If you do not have control of the server, then you will not be able to make this change. You would need to request it from the API provider.

Caplin

Actually the API is not mine, so I can't edit those..But why I can see them in the browser if I can't access?? – Watchmaker

And if I got this with php curl? – Watchmaker

I added a note about that; you'll need to request the API provider to add the header - although it's rather odd they enabled CORS without adding the header to expose the custom headers. Probably just an oversight. The browser is allowed to see everything. JS cannot in this case because of the Same Origin Policy – Caplin

If you get it with cURL through PHP then it will work fine as CORS will not be an issue. – Caplin

Seeing them in the browser is different than what xhr can retrieve. cURL should retrieve all headers so that might be the best option. – Lulualaba

Excellent. Thank you everybody! – Watchmaker

Answer 2

Your access specifier isn't mentioned, and therefore it does stores but at somewhat unknown place. Now you need to initialise it first. For better initialisation :

IN RESPONSE

 Acccess-Control-Expose-Headers: x-dl-units-left;

ON CLIENT SIDE

 $.ajax(ajaxConfig).done(function(response, textStatus, xhr){

  var all = xhr.getAllResponseHeaders(); 
 // "content-type: application/json;charset=UTF-8"

});

Radiotelegraphy

I'll try this asap – Watchmaker

You just need to declare and get value for left outside your function. – Radiotelegraphy