来自 React.js 应用程序的请求未命中 Node.js 后端端点

我正在制作

React

node

Node

3001

var port = normalizePort(process.env.PORT || '3001'); //in bin/www

React

"proxy": "http://localhost:3001", //in package.json

在

Node

app.js

/

app.use('/', indexRouter); //a path  with / goes to indexRouter

routes/index.js

var express = require('express');
var router = express.Router();
let index = require('../controllers/index');

/* GET home page. */
router.get('/', index.index);

module.exports = router;

controllers/index.js

json

exports.index = function(req, res, next) {
    console.log('index page'); //I DONT SEE THIS TRACE
    res.json({message: `some message` });
}

在

React

app.js

import React from "react";
import logo from './logo.svg';
import './App.css';

function App() {

  const [data, setData] = React.useState(null);

  React.useEffect(() => {
    fetch("/")
      .then((res) => {
        console.log(`got response ${res}`)
        res.json()}
        )
      .then((data) => {
        console.log(`data : ${data}`)
        setData(data.message)}
        );
  }, []);

  return (
    <div className="App">
      <header className="App-header">
        <img src={logo} className="App-logo" alt="logo" />
        <p>
          {!data ? "Loading..." : data}
        </p>
      </header>
    </div>
  );
}

export default App;

当我运行应用程序时（首先是

Node

React

console.log('index page');

controllers/index.js

我认为

react

node

App.js:12 got response [object Response]
App.js:16 data : undefined
App.js:17  Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'message')
    at App.js:17:1

进一步调试，我发现请求的响应是

304

请求是（url

/question