jquery ajax error

ajaxError.txt

$.ajax({
  type: 'GET',
  url: {url},
  success: function(data) {
    alert('Success');
  },
  error: function(xhr, textStatus, errorThrown) {
    if (xhr.readyState == 4) {
      // HTTP error (can be checked by XMLHttpRequest.status and XMLHttpRequest.statusText)
    } else if (xhr.readyState == 0) {
      // Network error (i.e. connection refused, access denied due to CORS, etc.)
    } else {
      // something weird is happening
    }
  }
});