create-react-app 脚手架解决本地跨域问题

背景：

用create-react-app 脚手架 搭建了一个新项目。但是开发过程中遇到跨域问题。报错：

Access to XMLHttpRequest at 'http://www.aaaa.com/' from origin 'http://localhost:3000' has been blocked by CORS policy: Request header field token is not allowed by Access-Control-Allow-Headers in preflight response.

解决方法：

1. npm install --save http-proxy-middleware
2. src目录下新建文件 setupProxy.js , 里面的内容如下

const {
    createProxyMiddleware } = require("http-proxy-middleware");

module.exports =