请阅读以下代码并解释其功能。javascript
const express = require('express);
const app = express;
//监听 GET请求,返回一个JSON 对象
app.get('/user',(req, res)=>{
res.send({ name:'zs', age: 20, gender:'男'});
});
//启动服务器,监听80端口
app.listen(80,()=>{
console.log('express server running at
http://127.0.0.1);
});