说说如何利用 Node.js 代理解决跨域问题

//代理const http = require('http');const request = require('request');const hostIp = '127.0.0.1';const apiPort = 8070;const imgPort = 8071;//创建 API 代理服务const apiServer = http.createServer((req, res) => {  console.log('[apiServer]req.url='+req.url);  const url = 'http://news-at.zhihu.com/story' + req.url;  console.log('[apiServer]url='+url);  const options = {    url: url  };  function callback(error, response, body) {    if (!error && response.statusCode === 200) {      //编码类型      res.setHeader('Content-Type', 'text/plain;charset=UTF-8');      //允许跨域      res.setHeader('Access-Control-Allow-Origin', '*');      //返回代理内容      res.end(body);    }  }  request.get(options, callback);});//监听 API 端口apiServer.listen(apiPort, hostIp, () => {  console.log('代理接口，运行于 http://' + hostIp + ':' + apiPort + '/');});//创建图片代理服务const imgServer = http.createServer((req, res) => {  const url = 'https://pic2.zhimg.com/' +req.url.split('/img/')[1];  console.log('[imgServer]url=' + url);  const options = {    url: url,    encoding: null  };  function callback(error, response, body) {    if (!error && response.statusCode === 200) {      const contentType = response.headers['content-type'];      res.setHeader('Content-Type', contentType);      res.setHeader('Access-Control-Allow-Origin', '*');      res.end(body);    }  }  request.get(options, callback);});//监听图片端口imgServer.listen(imgPort, hostIp, () => {  console.log('代理图片，运行于 http://' + hostIp + ':' + imgPort + '/')});