error-has been blocked by CORS policy:

先前用Vue開發時，有遇過用axios呼叫API時，發生 xxx has been blocked by CORS poicy: No Access-Control-Allow-Origin header is present on the requested resource.

解決方案

1.後端去改回傳的header
加上以下內容（不過有時後端不會想理你，主管又不夠力時此法無效XD）

header(‘Access-Control-Allow-Origin’, ‘*’) 
header(‘Access-Control-Allow-Methods’, ‘*’) 
header(‘Access-Control-Allow-Headers’, ‘Origin, Methods, Content-Type, Authorization’) 
header(‘Access-Control-Allow-Credentials’, true);

2.前端自己改
用vue-cli，建立項目，找到config/index.js檔案加上以下內容

module.exports = {
 dev:{
     ProxyTable: {
         '/data': {   // 自訂 local 端的位置
          target: 'http://data.taipei/',  // 遠端 URL Domain
          changeOrigin: true,
          pathRewrite: {
          '^/data': ''
          }
      }    
  }
}

Ref:
https://blog.csdn.net/weixin_44623040/article/details/94987738
https://ithelp.ithome.com.tw/questions/10199222
https://kuro.tw/posts/2017/06/07/%E5%A6%82%E4%BD%95%E5%9C%A8-Vue-CLI-%E5%BB%BA%E7%AB%8B%E7%9A%84%E9%96%8B%E7%99%BC%E7%92%B0%E5%A2%83%E5%91%BC%E5%8F%AB%E8%B7%A8%E5%9F%9F%E9%81%A0%E7%AB%AF-RESTful-APIs/