Webpack for js plugins

I’m writing a plugin on native JS and encountered a problem. When the development, Webpack works properly, I create a class and call it elsewhere. But I don’t need to call a class in production, and the Webpack just doesn’t process that code. How to force it to process code if this code is not called

const path = require('path');
const HTMLWebpackPlugin = require('html-webpack-plugin');
const CopyWebpackPlugin = require('copy-webpack-plugin');
const { CleanWebpackPlugin } = require('clean-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

const isDev = process.env.NODE_ENV === 'development';
const isProd = !isDev;

const fileName = ext => isDev ? `[name].${ext}` : `script.${ext}`;

module.exports = {
    context: path.resolve(__dirname, 'src'),
    mode: 'development',
    entry: {
        script: './index.js'
    },
    output: {
        filename: `js/${fileName('js')}`,
        path: path.resolve(__dirname, 'dist'),
        publicPath: ''
    },
    devServer: {
        historyApiFallback: true,
        contentBase: path.resolve(__dirname, 'dist'),
        open: true,
        compress: true,
        hot: true,
        port: 8080,
    },
    plugins: [
        new CleanWebpackPlugin(),
        new HTMLWebpackPlugin({
            template: path.resolve(__dirname, 'src/index.html'),
            filename: 'index.html',
        }),
        new MiniCssExtractPlugin({
            filename: `css/${fileName('css')}`
        }),
        new CopyWebpackPlugin({
            patterns: [{
               from: path.resolve(__dirname, 'src/img'),
                to: path.resolve(__dirname, 'dist/img')
            }]
         })
    ],
    devtool: isProd ? false : 'source-map',
    module: {
        rules: [
            {
                test: /.html$/i,
                loader: 'html-loader',
                options: {
                    minimize: {
                        removeComments: false,
                        collapseWhitespace: false,
                    },
                },
            },
            {
                test: /.css$/i,
                use: [{
                    loader: MiniCssExtractPlugin.loader,
                    options: {
                        hmr: isDev,
                        publicPath: '/'
                    }
                },
                    'css-loader',
                ],
            },
            {
                test: /.s[ac]ss$/i,
                use: [
                    {
                        loader: MiniCssExtractPlugin.loader,
                        options: {
                            publicPath: '/'
                        }
                    },
                    'css-loader',
                    'postcss-loader',
                    'sass-loader'
                ]
            },
            {
                test: /.js$/i,
                use: ['babel-loader'],
                exclude: /node_modules/
            },
            {
                test: /.(?:|gif|png|jpg|jpeg|svg)$/,
                use: [{
                    loader: 'file-loader',
                    options: {
                        name: 'img/[name].[ext]',
                    }
                }],
            }
        ]
    }
}