webpack.prod.js

const webpack = require('webpack');
const merge = require('webpack-merge');
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const OptimizeCssAssetsPlugin = require('optimize-css-assets-webpack-plugin');
const UglifyJsPlugin = require('uglifyjs-webpack-plugin');
const common = require('./webpack.common.js');

const commitHash = require('child_process')
    .execSync('git rev-parse --short HEAD')
    .toString()
    .trim();

module.exports = merge(common, {

    mode: 'production',
    module: {
        rules: [
            { test: /\.css$/, use: [ MiniCssExtractPlugin.loader, "css-loader" ]}
        ]
    },
    devtool: 'source-map',
    optimization: {
        minimizer: [
          new UglifyJsPlugin({
            cache: true,
            parallel: true,
            sourceMap: true
          }),
          new OptimizeCssAssetsPlugin({
            assetNameRegExp: /\.optimize\.css$/g,
            cssProcessor: require('cssnano'),
            cssProcessorOptions: { discardComments: {removeAll: true } },
            canPrint: true
        })
        ]
      },
    plugins: [
        new webpack.DefinePlugin({
            'process.env.NODE_ENV': JSON.stringify('production')
        }),
        new MiniCssExtractPlugin({
            filename: "[name].css",
            chunkFilename: "[id].css"
        }),
        new webpack.DefinePlugin({
            __COMMIT_HASH__: JSON.stringify(commitHash +  '-prod'),
        })
   ]
})