处理Ajax错误

Question

I have a function to upload a file using Ajax. It works fine in a normal situation. Now I'm trying to differentiate between a "Network error" and a "File does not exist error". The code looks basically like this:

$.ajax({
  type: 'PUT',
  url: upload_url,
  processData: false,
  data: selected_file,
  error: function(xhr, status, error) {
    logger.error("Error uploading file");
  }
});

This is what I've discovered so far:

In both cases, the parameters for the Ajax error function are very similar: xhr.status is 0, status is "error" and error is "".

I can clearly see different error codes in the Chrome console: net::ERR_INTERNET_DISCONNECTED and net::err_file_not_found but I can't/don't know how to find this codes from the Ajax error function.