CORS请求，Content-Type：application / json

Question

我正在开发一个带有React前端和节点后端的Web应用程序。它们分别在我的本地计算机上运行，分别在localhost:3000和localhost:8080上运行。是否可以使用headers: { "Content-Type": "application/json" }发出CORS请求？基于查看其他问题似乎是，但我仍然在控制台中收到错误：

Access to fetch at 'http://localhost:8080/chordSheets/0' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'.

我的代码是：React Component

    fetch(`http://localhost:8080/chordSheets/${id}`, {
      method: 'POST',
      credentials: 'include',
      mode: 'cors',
      body: data,
      headers: {
        "Content-Type": "application/json",
      },
    })

节点设置：

app.use((req, res, next) => {
  res.header("Access-Control-Allow-Origin", 'http://localhost:3000');
  res.header("Access-Control-Allow-Credentials", true);
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, Options");
  res.header('Access-Control-Allow-Methods', 'POST, GET, PUT, DELETE, OPTIONS');
  req.login = promisify(req.login, req);
  next();
});

如果我理解正确，这应该允许使用"Content-Type": "application/json"的CORS请求我不明白为什么控制台错误在设置为The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*'时说localhost:3000。

提前致谢。