ajax请求的Cors报头错误

const express = require('express');
const app = express();

app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*'); // 允许所有域，或指定特定域如 'http://example.com'
  res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
  res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization');
  if (req.method === 'OPTIONS') {
    res.sendStatus(200); // 对于预检请求直接返回成功
  } else {
    next();
  }
});

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

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

fetch('http://yourserver.com/data')
  .then(response => {
    if (!response.ok) {
      throw new Error('Network response was not ok ' + response.statusText);
    }
    return response.json();
  })
  .then(data => console.log(data))
  .catch(error => console.error('There has been a problem with your fetch operation:', error));