问在node.js中使用restful API和bodyParser时出错

EN

const express = require('express');
const app = express();
const bodyParser=require('body-parser');

app.use(bodyParser.json());


let profile = {
 username: 'azat',
 email: '[reducted]',
 url: 'http://azat.co'
 };
app.get('/profile', (req, res)=>{
  res.send(profile);
 })
app.post('/profile', (req, res) => {
    profile = req.body;
    console.log("created",profile);
    res.sendStatus(201);
 })
app.put('/profile', (req, res)=>{
    Object.assign(profile, req.body);
    console.log("updated",profile);
    res.sendStatus(204);
})
app.delete('/profile', (req, res)=>{
   profile ={};
   console.log("deleted");
   res.sendStatus(204);
})

app.listen(3000);