Webpack4 使用 async/await，webpack 支持 async/await，webpack打包支持ES7的async/await语法

npm install --save-dev @babel/plugin-transform-async-to-generator

下面两种方式二选一

1.  .babelrc 

{"plugins": ["@babel/plugin-transform-async-to-generator"]
}

2.  webpack.config.js   (here部分)

module: {rules: [{test: /\.js$/,use: [{loader: "eslint-loader",options: {enforce: "pre"}}],exclude: __dirname + "node_modules",include: __dirname + "src",},{test: /\.js$/,use: [{loader: "babel-loader",options: {presets: ["@babel/preset-env"],plugins: [// here"@babel/plugin-transform-async-to-generator","@babel/plugin-proposal-class-properties"]}}]}]}