webpack.build.js

const { merge } = require('webpack-merge')
const common = require('./webpack.config.js')
const TerserPlugIn = require('terser-webpack-plugin')
const CompressionPlugin = require('compression-webpack-plugin')

module.exports = merge(common, {
    mode: 'production',
    devtool: 'source-map',
    optimization: {
        minimizer: [
            new TerserPlugIn({
                terserOptions:{	
                    //sideEffects: false,
                    // All files have side effects, and none can be tree-shaken
                    // {
                    //   "./src/file2.js"
                    //  ]
                    // }
                    output:{
                        comments: false
                    }
                },
                parallel: true
            })
        ],
    },
    plugins: [
        new CompressionPlugin({
            test: /\.js(\?.*)?$/i,
        }),
    ],
    performance: {
        hints: "warning",
        // Calculates sizes of gziped bundles.
        assetFilter: function (assetFilename) {
            return assetFilename.endsWith(".js.gz");
        },
    }
})