出现 has been blocked by CORS policy: No ‘Access-Control-Allow-Origin‘ header is present on the 解决方法

1. 问题所示

执行代码的时候出现如下提示：

Access to XMLHttpRequest at 'http://127.0.0.1:5000/api/data' from origin 'http://10.197.0.79:8080' has been 
blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

截图如下所示：

2. 原理分析

错误信息表明浏览器阻止了来自不同源（Cross-Origin）的HTTP请求

由于跨源资源共享（CORS）策略的限制
CORS是一种浏览器安全机制，限制网页脚本能够