npm install babel-loader@8.0.0-beta.0 @babel/core @babel/preset-env webpack
webpack 3.x babel-loader 7.x | babel 6.x

var htmlWebpackPlugin = require('html-webpack-plugin')

const path = require('path')
module.exports = {
  mode: 'development',
  entry: './src/app.js',
  output: {
    filename: 'js/bundle.js',
    path: path.resolve(__dirname, 'dist')
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /(node_modules|bower_components)/, // (不处理node_modules 和 bower_components下的js文件) 优化处理加快速度
        use: {
          loader: 'babel-loader',
          options: {     // options选项中的presets设置的就是当前js的版本
            presets: ['@babel/preset-env']
          }
        }
      }
    ]
  },
  plugins: [
    new htmlWebpackPlugin({
      template: 'index.html',
      inject: 'body',
      filename: 'index.html'
    })
  ]
}