无法识别CORS标头

我在开发Vue.js应用程序时遇到了一个有趣的问题。

开发环境

  1. I use yarn serve to start the localhost:8080.
  2. In one of the Vue files, I use fetch to call a remote API.
fetch(uri).then(res=>{
  return res.json();
}).then(json => {
  this.summary=json;
  console.log(json);
})
  1. If the uri is api/rsywx/.../xxx/, where api is a referring to a Vagrant machine booted up in my development machine with a different IP. My machine is in 192.168.0.x and my Vagrant machine is in 192.168.3.x. This works fine. The remote data returns correctly.

  2. If the uri is api.rsywx.com/rsywx/.../xxx, where I only switched the host part to my actual API server, it comes back with a famous CORS error.

However, if I check the header returned from api and api.rsywx.com, the both contain the following lines:

enter image description here

(我同时使用Fx和Chrome)

所以一定有我不知道的东西。有人可以给我一些提示吗?

非常感激。