Webpack with Sass, PostCSS and JavaScript/JSX

.babelrc

{
  "presets": ["env", "react"]
}

package.json

{
  "name": "sample",
  "version": "1.0.0",
  "description": "Sample",
  "main": "index.js",
  "scripts": {
    "test": "jest",
    "dev": "webpack-dev-server",
    "build": "webpack"
  },
  "devDependencies": {
    "autoprefixer": "^7.1.6",
    "babel": "^6.23.0",
    "babel-loader": "^7.1.2",
    "babel-preset-env": "^1.6.1",
    "babel-preset-react": "^6.24.1",
    "css-loader": "^0.28.7",
    "cssnano": "^3.10.0",
    "extract-text-webpack-plugin": "^3.0.2",
    "jest": "^21.2.1",
    "node-sass": "^4.5.3",
    "postcss": "^6.0.14",
    "postcss-loader": "^2.0.8",
    "sass-loader": "^6.0.6",
    "webpack": "^3.8.1",
    "webpack-dev-server": "^2.9.4"
  }
}

postcss.config.js

module.exports = {
    plugins: [
        require('autoprefixer'),
        require('cssnano')
    ]
};

webpack.config.js

const path = require('path');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const UglifyJSPlugin = require('uglifyjs-webpack-plugin');

module.exports = {
    entry: {
        app: ['./src/js/index.js', './src/css/master.scss']
    },
    output: {
        path: path.resolve(__dirname, 'dist'),
        filename: '[name].js'
    },
    module: {
        loaders: [
            { test: /\.js$/, loader: 'babel-loader', exclude: /node_modules/ },
            { test: /\.jsx$/, loader: 'babel-loader', exclude: /node_modules/ }
        ],
        rules: [
            {
                test: /\.scss$/,
                use: ExtractTextPlugin.extract({
                    use: [{loader: 'css-loader', options: {importLoaders: 1}}, {loader: 'postcss-loader'}, {loader: 'sass-loader'}]
                })
            }
        ]
    },
    plugins: [
        new ExtractTextPlugin('style.css', {allChunks: true}),
        new UglifyJSPlugin()
    ]
};