webpack.prod.js

const webpack = require('webpack');
const merge = require('webpack-merge');
const UglifyJSPlugin = require('uglifyjs-webpack-plugin');
const common = require('./webpack.common.js');
const ExtractTextPlugin = require("extract-text-webpack-plugin");

const extractSass = new ExtractTextPlugin({
    filename: "[name].[contenthash].css",
    disable: process.env.NODE_ENV === "development"
});

module.exports = merge(common, {
    devtool: 'source-map',
    module: {
        rules: [{
            test: /\.scss$/,
            use: extractSass.extract({
                use: [{
                    loader: "css-loader"
                }, {
                    loader: "sass-loader"
                }],
                // use style-loader in development
                fallback: "style-loader"
            })
        }]
    },
    plugins: [
        new UglifyJSPlugin({
            sourceMap: true
        }),
        new webpack.DefinePlugin({
            'process.env': {
                'NODE_ENV': JSON.stringify('production')
            }
        }),
        extractSass
    ],
    output: {
        publicPath: '/'
    }
});