C:\tools\nginx-1.28.0\conf\nginx.conf文件，报错：Access to fetch at 'http://localhost/api-aa2-agent12/classes/courses' from origin 'http://localhost:3001' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.

修改说明

为什么需要处理 OPTIONS 请求？

当浏览器发起跨域请求时，会先发送一个 OPTIONS 预检请求（preflight request）来检查服务器是否允许实际请求。如果 Nginx 不正确处理这个 OPTIONS 请求，浏览器就会报 CORS 错误。

主要改进：

1. 单独处理 OPTIONS 请求，直接返回 204 状态码
2. 所有 CORS 头添加 always 参数，确保在所有响应中都包含
3. 增加了 Authorization 头的支持，允许传递 token

重新加载 Nginx 后，CORS 错误应该就解决了！

    server {
        listen 80;
        server_name localhost;
        location /api-aa2-agent12/ {

            # 处理 OPTIONS 预检请求
            if ($request_method = 'OPTIONS') {
                add_header 'Access-Control-Allow-Origin' '*' always;
                add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, PATCH, OPTIONS' always;
                add_header 'Access-Control-Allow-Headers' 'Authorization, Content-Type, Accept, Origin, User-Agent, DNT, Cache-Control, X-Mx-ReqToken, X-Requested-With' always;
                add_header 'Access-Control-Max-Age' 1728000 always;
                add_header 'Content-Type' 'text/plain; charset=utf-8' always;
                add_header 'Content-Length' 0 always;
                return 204;
            }

            # 设置允许跨域的域，* 表示允许任何域，也可以设置特定的域
            add_header 'Access-Control-Allow-Origin' '*' always;
            # 允许的方法
            add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, PATCH, OPTIONS' always;
            # 允许的头信息字段
            add_header 'Access-Control-Allow-Headers' 'Authorization, Content-Type, Accept, Origin, User-Agent, DNT, Cache-Control, X-Mx-ReqToken, X-Requested-With' always;
            # 缓存时间
            add_header 'Access-Control-Max-Age' 1728000 always;


            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header REMOTE-HOST $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-NginX-Proxy true;

            proxy_set_header Connection '';
            proxy_http_version 1.1;
            chunked_transfer_encoding off;
            proxy_buffering off;
            proxy_cache off;

            proxy_pass http://192.168.31.141:1234/;
        }
    }