css压缩

对于 webpack5 及以上，我们要使用到 css-minimizer-webpack-plugin 插件

const CssMinimizerWebpackPlugin = require('css-minimizer-webpack-plugin')
const MiniCssExtractPlugin = require('mini-css-extract-plugin')
module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader',
          {
            loader: "postcss-loader",
            options: {
              postcssOptions: {
                plugins: [
                  [
                    "postcss-preset-env"
                  ]
                ]
              }
            }
          }
        ]
      }
    ]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: 'css/built.css'
    })
  ],
  optimization: {
    minimizer: [
      new CssMinimizerWebpackPlugin()
    ],
    // css压缩仅在生产模式上生效
    // 如果想在开发模式上运行，必须将optimization.minimize设置为true
    minimize: true
  }
}