二级域名跨域问题

// 服务器端示例（Node.js + Express）
const express = require('express');
const app = express();

app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', 'https://subdomain.example.com');
  res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE');
  res.header('Access-Control-Allow-Headers', 'Content-Type');
  next();
});

app.get('/data', (req, res) => {
  res.json({ message: 'Hello from server!' });
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

<!-- 前端示例 -->
<script>
function handleResponse(data) {
  console.log(data.message);
}

const script = document.createElement('script');
script.src = 'https://subdomain.example.com/data?callback=handleResponse';
document.body.appendChild(script);
</script>

// 代理服务器示例（Node.js + Express）
const express = require('express');
const { createProxyMiddleware } = require('http-proxy-middleware');

const app = express();

app.use('/api', createProxyMiddleware({
  target: 'https://subdomain.example.com',
  changeOrigin: true,
  pathRewrite: {
    '^/api': ''
  }
}));

app.listen(3000, () => {
  console.log('Proxy server is running on port 3000');
});

// 前端示例
const socket = new WebSocket('wss://subdomain.example.com/socket');

socket.onopen = () => {
  socket.send('Hello from client!');
};

socket.onmessage = (event) => {
  console.log(event.data);
};