错误页面不缓存

@@ -5,15 +5,22 @@
 const headerModel = require('../models/header');
 const logger = global.yoho.logger;
 
-exports.notFound = () => {
-    return (req, res) => {
-        res.status(404);
-
+const forceNoCache = (res) => {
+    if (res) {
         res.set({
             'Cache-Control': 'no-cache',
             Pragma: 'no-cache',
             Expires: (new Date(1900, 0, 1, 0, 0, 0, 0)).toUTCString()
         });
+    }
+};
+
+
+exports.notFound = () => {
+    return (req, res) => {
+        forceNoCache(res);
+
+        res.status(404);
 
         if (req.xhr) {
             return res.json({
@@ -40,11 +47,7 @@ exports.notFound = () => {
  */
 exports.serverError = () => {
     return (err, req, res, next) => {
-        res.set({
-            'Cache-Control': 'no-cache',
-            Pragma: 'no-cache',
-            Expires: (new Date(1900, 0, 1, 0, 0, 0, 0)).toUTCString()
-        });
+        forceNoCache(res);
 
         logger.error(`error at path: ${req.url}`);
         logger.error(err);