Analyze the problems encountered when upgrading webpack3 to webpack4 version (summary)

const VueLoaderPlugin = require('vue-loader/lib/plugin')  ++++
const MiniCssExtractPlugin = require('mini-css-extract-plugin')   // webpack 4  +++

const ExtractTextPlugin = require('extract-text-webpack-plugin') //for webpack3  -----

module.exports = {
...
plugins: [
        + new VueLoaderPlugin(),  ++++
        + new MiniCssExtractPlugin({filename:'mian.css'})  //for webpack 4 +++
         - new ExtractTextPlugin({filename:'main.css'}) //for webpack 3 ---
]
...
}

devServer: {
     ++ contentBase: path.resolve(__dirname, '../dos-html'),  // 需要指定路径 ++
        port: 7001,
        hot: true,
        // open: false,
        inline: true,
        compress: true,
        historyApiFallback: true,
       ....
    },

plugins: [
   //已经移除
   new webpack.optimize.CommonsChunkPlugin({
       name: 'vendor',
       minChunks: function (module) {
         // any required modules inside node_modules are extracted to vendor
         return (
           module.resource && /\.js$/.test(module.resource) &&
           module.resource.indexOf( path.join(__dirname, '../node_modules')) === 0
         )
       }
     }),
   new webpack.optimize.UglifyJsPlugin(...）//已经移除
}

// ===> 修改为以下

const UglifyJsPlugin = require('uglifyjs-webpack-plugin');

moudel.exports = {

mode: 'production', ++ 这里指定模式。
...
optimization: {
    splitChunks: {
      name(module) {
        return (
          module.resource && /\.js$/.test(module.resource) &&
          module.resource.indexOf(path.join(__dirname, '../node_modules')) === 0
        )
      }
    },
    minimize: true,
    minimizer: [
      new UglifyJsPlugin({
        uglifyOptions: {
          compress: {
            warnings: false,
            // drop_debugger: true,
            // drop_console: true
          },
          sourceMap: false
        }
      })
    ]
  },
...
}