webpack.config.js

const path = require('path');
const MiniCssExtractPlugin = require("mini-css-extract-plugin")
const OptimizeCssAssetsPlugin = require('optimize-css-assets-webpack-plugin')

module.exports = {
  entry: {
    main: './src/main.js'
  },
  output: {
    filename: '[name].js',
    path: path.resolve(__dirname, 'assets')
  },
  module: {
    rules: [{
      test: /\.scss$/,
      use: [
        {
          loader: MiniCssExtractPlugin.loader,
          options: {
            publicPath: './assets/'
          }
        },
        "css-loader",
        "sass-loader"
      ]
    }]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css"
    }),
    new OptimizeCssAssetsPlugin({
      assetNameRegExp: /\.css$/g,
      cssProcessor: require('cssnano'),
      cssProcessorOptions: { safe: true, discardComments: { removeAll: true } },
     canPrint: true
    })
  ]
};