使用async函数，在webpack打包时报错
babel-polyfill is required. You must also install it in order to get async/await working.
需要加入babel-polyfill
npm i -D babel-polyfill
这里有个小插曲，经测试发现yarn 无法安装css-loader 1.0.0，
而且若先用npm安装完css-loader后用yarn安装其他包也会报错，可用npm安装
在webpack.config.js 的entry选项中
entry: ['babel-polyfill',join("./src/main.js")],
参考链接：https://*.com/questions/33527653/babel-6-regeneratorruntime-is-not-defined