How to use Terser with webpack

Question

I am using Webpack 6.10.2 with Vue 3.9.3. This install uses Uglify.js which throws an error when I run npm run build because it cannot work with ES6.

To get round this, I have removed Uglify form webpack.config.js as recommended and I have attempted to use Terser to minify the JS in production. Every attempt I have made results in errors because I haven't added the syntax right. When I remove Terser, the app compiles but obviously without JS minification so I am doing something wrong with the syntax in webpack.config.js.

Can anyone tell me where I am going wrong.

Thank you

webpack.config.js :

var path = require('path')
var webpack = require('webpack')
const TerserPlugin = require('terser-webpack-plugin')

module.exports = {
  entry: './src/main.js',
  output: {
    path: path.resolve(__dirname, './dist'),
    publicPath: '/dist/',
    filename: 'build.js'
  },
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          'vue-style-loader',
          'css-loader'
        ],
      },
      {
        test: /\.scss$/,
        use: [
          'vue-style-loader',
          'css-loader',
          'sass-loader'
        ],
      },
      {
        test: /\.sass$/,
        use: [
          'vue-style-loader',
          'css-loader',
          'sass-loader?indentedSyntax'
        ],
      },
      {
        test: /\.vue$/,
        loader: 'vue-loader',
        options: {
          loaders: {
            // Since sass-loader (weirdly) has SCSS as its default parse mode, we map
            // the "scss" and "sass" values for the lang attribute to the right configs here.
            // other preprocessors should work out of the box, no loader config like this necessary.
            'scss': [
              'vue-style-loader',
              'css-loader',
              'sass-loader'
            ],
            'sass': [
              'vue-style-loader',
              'css-loader',
              'sass-loader?indentedSyntax'
            ]
          }
          // other vue-loader options go here
        }
      },
      {
        test: /\.js$/,
        loader: 'babel-loader',
        exclude: /node_modules/
      },
      {
        test: /\.(png|jpg|gif|svg)$/,
        loader: 'file-loader',
        options: {
          name: '[name].[ext]?[hash]'
        }
      }
    ]
  },
  resolve: {
    alias: {
      'vue$': 'vue/dist/vue.esm.js'
    },
    extensions: ['*', '.js', '.vue', '.json']
  },
  devServer: {
    historyApiFallback: true,
    noInfo: true,
    overlay: true
  },
  performance: {
    hints: false
  },
  devtool: '#eval-source-map'
}

if (process.env.NODE_ENV === 'production') {
  module.exports = {
    optimization: )
    minimizer: [new TerserPlugin()],
  },
  module.exports.devtool = '#source-map'
  module.exports.plugins = (module.exports.plugins || []).concat([
    new webpack.DefinePlugin({
      'process.env': {
        NODE_ENV: '"production"'
      }
    }),
    new webpack.LoaderOptionsPlugin({
      minimize: true
    })
  ])
}

package.json :

{
  "name": "vue_frontend",
  "description": "A Vue.js project",
  "version": "1.0.0",
  "author": "Thomas Bishop <[email protected]>",
  "license": "MIT",
  "private": true,
  "scripts": {
    "dev": "cross-env NODE_ENV=development webpack-dev-server --open --hot",
    "build": "cross-env NODE_ENV=production webpack --progress --hide-modules"
  },
  "dependencies": {
    "buefy": "^0.7.10",
    "vue": "^2.5.11",
    "vue-router": "^3.0.7"
  },
  "browserslist": [
    "> 1%",
    "last 2 versions",
    "not ie <= 8"
  ],
  "devDependencies": {
    "babel-core": "^6.26.0",
    "babel-loader": "^7.1.2",
    "babel-preset-env": "^1.6.0",
    "babel-preset-stage-3": "^6.24.1",
    "cross-env": "^5.0.5",
    "css-loader": "^0.28.7",
    "file-loader": "^1.1.4",
    "node-sass": "^4.5.3",
    "sass-loader": "^6.0.6",
    "terser-webpack-plugin": "^1.4.1",
    "vue-loader": "^13.0.5",
    "vue-template-compiler": "^2.4.4",
    "webpack": "^3.6.0",
    "webpack-dev-server": "^2.9.1"
  }
}

Solution 1

 optimization: {
  removeAvailableModules: false,
   minimizer: [
    new TerserJSPlugin({
      terserOptions: {
        parse: {
          // we want terser to parse ecma 8 code. However, we don't want it
          // to apply any minfication steps that turns valid ecma 5 code
          // into invalid ecma 5 code. This is why the 'compress' and 'output'
          // sections only apply transformations that are ecma 5 safe
          // https://github.com/facebook/create-react-app/pull/4234
          ecma: 8
        },
        compress: {
          ecma       : 5,
          warnings   : false,
          // Disabled because of an issue with Uglify breaking seemingly valid code:
          // https://github.com/facebook/create-react-app/issues/2376
          // Pending further investigation:
          // https://github.com/mishoo/UglifyJS2/issues/2011
          comparisons: false,
          // Disabled because of an issue with Terser breaking valid code:
          // https://github.com/facebook/create-react-app/issues/5250
          // Pending futher investigation:
          // https://github.com/terser-js/terser/issues/120
          inline     : 2
        },
        mangle: {
          safari10: true
        },
        output: {
          ecma      : 5,
          comments  : false,
          // Turned on because emoji and regex is not minified properly using default
          // https://github.com/facebook/create-react-app/issues/2488
          ascii_only: true
        }
      },
      cache: true,
      parallel: true,
      sourceMap: true, // Must be set to true if using source-maps in production
    }),
    new OptimizeCSSAssetsPlugin({})
],
runtimeChunk: true
},

Solution 2

As of webpack 5 all u need is to add this syntax to extend existing minimizers which is terser one of them. https://webpack.js.org/plugins/css-minimizer-webpack-plugin/

minimizer: [
  // this `...` do that for you
  `...`,
 // your other minimizers goes here
  new CssMinimizerPlugin({
    exclude: /(node_modules)/,
  }),
],