商城怎么使用ajax?

Ajax.call('order.php?act=export', params, function (data) {
          document.getElementById("export").disabled = false;
          document.getElementById("export").value = "导出到Excel";
          document.location.href = (data.url);
      }, 'POST', 'JSON');

$response = array('url' => $fileName,'success'=>true);
echo json_encode($response);