Firefox 和 Internet Explorer 在 OPTIONS 请求后收到 200 OK 后不发送 POST 请求 - 在 Chrome 中工作正常

浏览器间的差异：OPTIONS请求导致Firefox和Internet Explorer未发送POST请求

javascript
// Express框架的Node.js服务器示例
const express = require('express');
const app = express();
// 允许跨域请求
app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
  res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');
  next();
});
// 处理POST请求
app.post('/example', (req, res) => {
  // 处理POST请求的逻辑
  res.send('POST请求成功！');
});
// 启动服务器
const port = 3000;
app.listen(port, () => {
  console.log(`服务器运行在 http://localhost:${port}`);
});

javascript
const xhr = new XMLHttpRequest();
xhr.open('POST', 'http://localhost:3000/example', true);
xhr.setRequestHeader('Content-Type', 'application/json');
xhr.onreadystatechange = function () {
  if (xhr.readyState === XMLHttpRequest.DONE) {
    if (xhr.status === 200) {
      console.log('POST请求成功！');
    } else {
      console.error('POST请求失败。');
    }
  }
};
// 发送请求
xhr.send(JSON.stringify({ key: 'value' }));

javascript
// 处理OPTIONS请求
app.options('/example', (req, res) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
  res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');
  res.sendStatus(200);
});

javascript
const cors = require('cors');
app.use(cors());