省钱秘笈之巧用Cloudflare免费做个镜像网站

偶然看到一个利用 Cloudflare Workers 做镜像的方法，无须购买服务器了，留作备用。
GitHub 项目：https://github.com/Siujoeng-Lau/Workers-Proxy

1. 如果已经注册了 Cloudflare 账号，直接在左上 Products->Workers，没有就注册一个账号再说。
2. 填写一个唯一子域名，Set up：
   
3. 选择免费版：
   
4. 点击 Create a Worker 创建一个 Worker：
   
5. 自动生成一串名称，有 hello world 示例代码：
   

6. 删除示例，拷贝下方代码，看预览，保存部署：
   

   // 代理网站.
   const upstream = 'www.google.com'
   
   // 代理网站的目录.
   const upstream_path = '/'
   
   // 手机用户代理网站.
   const upstream_mobile = 'www.google.com'
   
   // 屏蔽国家和地区.
   const blocked_region = ['KP', 'SY', 'PK', 'CU']
   
   // 屏蔽 IP 地址.
   const blocked_ip_address = ['0.0.0.0', '127.0.0.1']
   
   // 源站是否开启 HTTPS.
   const https = true
   
   // 文本替换.
   const replace_dict = {
       '$upstream': '$custom_domain',
       '//google.com': ''
   }
   
   addEventListener('fetch', event => {
       event.respondWith(fetchAndApply(event.request));
   })
   
   async function fetchAndApply(request) {
   
       const region = request.headers.get('cf-ipcountry').toUpperCase();
       const ip_address = request.headers.get('cf-connecting-ip');
       const user_agent = request.headers.get('user-agent');
   
       let response = null;
       let url = new URL(request.url);
       let url_hostname = url.hostname;
   
       if (https == true) {
           url.protocol = 'https:';
       } else {
           url.protocol = 'http:';
       }
   
       if (await device_status(user_agent)) {
           var upstream_domain = upstream;
       } else {
           var upstream_domain = upstream_mobile;
       }
   
       url.host = upstream_domain;
       if (url.pathname == '/') {
           url.pathname = upstream_path;
       } else {
           url.pathname = upstream_path + url.pathname;
       }
   
       if (blocked_region.includes(region)) {
           response = new Response('Access denied: WorkersProxy is not available in your region    yet.', {
               status: 403
           });
       } else if (blocked_ip_address.includes(ip_address)) {
           response = new Response('Access denied: Your IP address is blocked by WorkersProxy.',   {
               status: 403
           });
       } else {
           let method = request.method;
           let request_headers = request.headers;
           let new_request_headers = new Headers(request_headers);
   
           new_request_headers.set('Host', url.hostname);
           new_request_headers.set('Referer', url.hostname);
   
           let original_response = await fetch(url.href, {
               method: method,
               headers: new_request_headers
           })
   
           let original_response_clone = original_response.clone();
           let original_text = null;
           let response_headers = original_response.headers;
           let new_response_headers = new Headers(response_headers);
           let status = original_response.status;
   
           new_response_headers.set('access-control-allow-origin', '*');
           new_response_headers.set('access-control-allow-credentials', true);
           new_response_headers.delete('content-security-policy');
           new_response_headers.delete('content-security-policy-report-only');
           new_response_headers.delete('clear-site-data');
   
           const content_type = new_response_headers.get('content-type');
           if (content_type.includes('text/html') && content_type.includes('UTF-8')) {
               original_text = await replace_response_text(original_response_clone,    upstream_domain, url_hostname);
           } else {
               original_text = original_response_clone.body
           }
   
           response = new Response(original_text, {
               status,
               headers: new_response_headers
           })
       }
       return response;
   }
   
   async function replace_response_text(response, upstream_domain, host_name) {
       let text = await response.text()
   
       var i, j;
       for (i in replace_dict) {
           j = replace_dict[i]
           if (i == '$upstream') {
               i = upstream_domain
           } else if (i == '$custom_domain') {
               i = host_name
           }
   
           if (j == '$upstream') {
               j = upstream_domain
           } else if (j == '$custom_domain') {
               j = host_name
           }
   
           let re = new RegExp(i, 'g')
           text = text.replace(re, j);
       }
       return text;
   }
   
   
   async function device_status(user_agent_info) {
       var agents = ["Android", "iPhone", "SymbianOS", "Windows Phone", "iPad", "iPod"];
       var flag = true;
       for (var v = 0; v < agents.length; v++) {
           if (user_agent_info.indexOf(agents[v]) > 0) {
               flag = false;
               break;
           }
       }
       return flag;
   }

7. 返回可重命名，这时就可以直接访问 WorkerName.Subdomain.workers.dev 了：
   
8. 觉得域名太长不太好记，可以用自己的域名，前提是要在 cloudflare 解析，选择域名，点击 Workers->Add router：
   
9. Route 填 subdomain.yourdomain.com/* ，Worker 选择前面的部署：
   
10. 在域名 DNS 解析里新建一个 CNAME 记录指向 WorkerName.Subdomain.workers.dev，等待生效后就可以用自己的域名访问了：
    
11. 有时候会出现下面这个界面，等一会或者换个浏览器再看看：
    

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