js
const { CleanWebpackPlugin } = require('clean-webpack-plugin');

const webpackConfig = {
    plugins: [
        /**
         * All files inside webpack's output.path directory will be removed once, but the
         * directory itself will not be. If using webpack 4+'s default configuration,
         * everything under <PROJECT_DIR>/dist/ will be removed.
         * Use cleanOnceBeforeBuildPatterns to override this behavior.
         *
         * During rebuilds, all webpack assets that are not used anymore
         * will be removed automatically.
         *
         * See `Options and Defaults` for information
         */
        new CleanWebpackPlugin(),
    ],
};

module.exports = webpackConfig;

js
new CleanWebpackPlugin({
    // Simulate the removal of files
    //
    // default: false
    dry: true,

    // Write Logs to Console
    // (Always enabled when dry is true)
    //
    // default: false
    verbose: true,

    // Automatically remove all unused webpack assets on rebuild
    //
    // default: true
    cleanStaleWebpackAssets: false,

    // Do not allow removal of current webpack assets
    //
    // default: true
    protectWebpackAssets: false,

    // **WARNING**
    //
    // Notes for the below options:
    //
    // They are unsafe...so test initially with dry: true.
    //
    // Relative to webpack's output.path directory.
    // If outside of webpack's output.path directory,
    //    use full path. path.join(process.cwd(), 'build/**/*')
    //
    // These options extend del's pattern matching API.
    // See https://github.com/sindresorhus/del#patterns
    //    for pattern matching documentation

    // Removes files once prior to Webpack compilation
    //   Not included in rebuilds (watch mode)
    //
    // Use !negative patterns to exclude files
    //
    // default: ['**/*']
    cleanOnceBeforeBuildPatterns: [
        '**/*',
        '!static-files*',
        '!directoryToExclude/**',
    ],
    cleanOnceBeforeBuildPatterns: [], // disables cleanOnceBeforeBuildPatterns

    // Removes files after every build (including watch mode) that match this pattern.
    // Used for files that are not created directly by Webpack.
    //
    // Use !negative patterns to exclude files
    //
    // default: []
    cleanAfterEveryBuildPatterns: ['static*.*', '!static1.js'],

    // Allow clean patterns outside of process.cwd()
    //
    // requires dry option to be explicitly set
    //
    // default: false
    dangerouslyAllowCleanPatternsOutsideProject: true,
});

js
const { CleanWebpackPlugin } = require('clean-webpack-plugin'); // installed via npm
const HtmlWebpackPlugin = require('html-webpack-plugin'); // installed via npm
const webpack = require('webpack'); // to access built-in plugins
const path = require('path');

module.exports = {
    entry: './path/to/my/entry/file.js',
    output: {
        /**
         * With zero configuration,
         *   clean-webpack-plugin will remove files inside the directory below
         */
        path: path.resolve(process.cwd(), 'dist'),
    },
    module: {
        rules: [
            {
                test: /\.(js|jsx)$/,
                loader: 'babel-loader',
            },
        ],
    },
    plugins: [
        new webpack.ProgressPlugin(),
        new CleanWebpackPlugin(),
        new HtmlWebpackPlugin({ template: './src/index.html' }),
    ],
};