docs: update issue 237

archives/2023/237.md

@@ -0,0 +1,22 @@
+---
+title: 解决跨域问题 Response to preflight request doesn't pass access control check
+number: '#237'
+link: 'https://github.com/toFrankie/blog/issues/237'
+created_at: '2023-02-26 19:06:25'
+updated_at: '2024-03-23 00:47:56'
+labels:
+  - 前端
+  - Ajax
+  - '2021'
+---
+对于前后端分离，跨域问题老生常谈了，问题是这样的：
+
+> Access to fetch at 'https://xxx/api/user' from origin 'http://h5.xxx.com' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: The 'Access-Control-Allow-Origin' header contains multiple values 'http://h5.xxx.com, *', but only one is allowed. Have the server send the header with a valid value, or, if an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
+
+翻译过来就是：
+
+> 从源 `http://h5.xxx.com` 访问 `https://xxx/api/user` 处的访存已被 CORS 策略阻止：对预检请求的响应未通过访问控制检查：`Access-Control-Allow-Origin` 标头包含多个值 `http://h5.xxx.com, *`，但仅允许一个。 让服务器发送带有有效值的标头，或者，如果不透明的响应满足您的需要，请将请求的模式设置为 `no-cors`，以在禁用 CORS 的情况下获取资源。
+
+原因是就是在服务器设置了允许跨域，同时又在 Nginx 代理又设置了一次。
+
+只要移除其一即可解决。