我有一个使用 React、Node.js 和 Socket.io 制作的应用程序

我将 Node 后端部署到 heroku ，前端部署到 Netlify

我知道 CORS 错误与服务器有关，但无论我添加什么，它都无法解决下图中的错误。

我还在 React 的 package.json 中添加了代理脚本作为“proxy”：“https://googledocs-clone-sbayrak.herokuapp.com/”

这是我的 server.js 文件；

const mongoose = require('mongoose');
const Document = require('./Document');
const dotenv = require('dotenv');
const path = require('path');
const express = require('express');
const http = require('http');
const socketio = require('socket.io');
dotenv.config();

const app = express();
app.use(cors());
const server = http.createServer(app);
const io = socketio(server, {
  cors: {
    origin: 'https://googledocs-clone-sbayrak.netlify.app/',
    methods: ['GET', 'POST'],
  },
});

app.get('/', (req, res) => {
  res.status(200).send('hello!!');
});

const connectDB = async () => {
  try {
    const connect = await mongoose.connect(process.env.MONGODB_URI, {
      useUnifiedTopology: true,
      useNewUrlParser: true,
    });

    console.log('MongoDB Connected...');
  } catch (error) {
    console.error(`Error : ${error.message}`);
    process.exit(1);
  }
};

connectDB();


let defaultValue = '';

const findOrCreateDocument = async (id) => {
  if (id === null) return;

  const document = await Document.findById({ _id: id });

  if (document) return document;

  const result = await Document.create({ _id: id, data: defaultValue });
  return result;
};
io.on('connection', (socket) => {
  socket.on('get-document', async (documentId) => {
    const document = await findOrCreateDocument(documentId);
    socket.join(documentId);
    socket.emit('load-document', document.data);
    socket.on('send-changes', (delta) => {
      socket.broadcast.to(documentId).emit('receive-changes', delta);
    });

    socket.on('save-document', async (data) => {
      await Document.findByIdAndUpdate(documentId, { data });
    });
  });
  console.log('connected');
});

server.lis ten(process.env.PORT || 5000, () =>
  console.log(`Server has started.`)
);

这是我向前端发出请求的地方；

import Quill from 'quill';
import 'quill/dist/quill.snow.css';
import { useParams } from 'react-router-dom';
import { io } from 'socket.io-client';

const SAVE_INTERVAL_MS = 2000;
 

const TextEditor = () => {
  const [socket, setSocket] = useState();
  const [quill, setQuill] = useState();
  const { id: documentId } = useParams();

  useEffect(() => {
    const s = io('https://googledocs-clone-sbayrak.herokuapp.com/');
    setSocket(s);
     

    return () => {
      s.disconnect();
    };
  }, []); 

 /* below other functions */
 /* below other functions */
 /* below other functions */
 }