Organising webpack config

webpack.blocks.js

const dependencyCssRule = {

};

function sassRule(options) {
  return {
    test: 1,
    use: [
      // use options.prod to turn off sourcemaps
      // use options.prod to set sass outputStyle compressed/not
    ]
  };
}

module.exports = { dependencyCssRule, sassRule };

webpack.config.common.js

module.exports = (env, argv, options) => {

  return {
    context: 1,
    entry: 1,
    externals: 1,

    module: {
      rules: [

      ]
    },

    output: 1,

    resolve: {
      modules: [
        path.resolve(rootPath, 'src'),  // avoid ../.. hell in imports
        'node_modules',
      ]
    }
  };
};

webpack.config.dev.js

const blocks = require('./webpack.blocks');
const createCommonConfig = require('./webpack.config.common');

module.exports = (env, argv) => {

  const options = {};
  const commonConfig = createCommonConfig(env, argv, options);
  const sassRule = configBlocks.sassRule(options);

  return {
    ...commonConfig,

    devServer: 1,
    devtool: 1,
    mode: 'development',

    module: {
      rules: [
        ...commonConfig.module.rules,
        configBlocks.dependencyCssRule,
        { }, {
          test: sassRule.test,
          use: [
            'style-loader',
            ...sassRule.use,
          ]
        }
      ]
    },

    performance: 1,
    plugins: 1,
  };
};

webpack.config.prod.js

module.exports = (env, argv) => {

  const options = { prod: true };
  const commonConfig = createCommonConfig(env, argv, options);
  const sassRule = configBlocks.sassRule(options);

  return {
    ...commonConfig,

    bail: 1,
    devtool: 1,
    mode: 'production',

    module: {
      rules: [
        ...commonConfig.module.rules,
        {
          test: sassRule.test,
          use: ExtractTextWebpackPlugin.extract({
            use: sassRule.use,
          }),
        }
      ]
    },

    optimization: 1,  // uglify: no parallel, sourcemep true, warningsFilter sourceAbsPath && !includes 'node_modules' uglifyOptions output.comments=some, warnings=true

    output: {
      ...commonConfig.output,
      path: rootPath,
    },

    performance: 1,

    plugins: 1,
  };
}