const express=require('express');var server=express();server.use('/a.html',function (req,res) {    res.send('ok').end();})server.get('/b.html',function (req,res) {    res.writeHead(200, {'Content-Type': 'text/html; charset=utf-8'});//只需要设置响应头的编码格式就好    res.write('write只能写字符串和buffer');    console.log(res.writeHead);    res.end();})server.listen(8080);```