webpack.mix.js

const mix = require('laravel-mix');

/*
 |--------------------------------------------------------------------------
 | Mix Asset Management
 |--------------------------------------------------------------------------
 |
 | Mix provides a clean, fluent API for defining some Webpack build steps
 | for your Laravel application. By default, we are compiling the Sass
 | file for the application as well as bundling up all the JS files.
 |
 */

var webpack = require('webpack');

mix.webpackConfig({
    resolve: {
        extensions: ['.js', '.jsx']
    },
    plugins: [
        new webpack.DefinePlugin({ // <-- key to reducing React's size
            'process.env': {
                'NODE_ENV': JSON.stringify('production')
            }
        }),
        new webpack.optimize.AggressiveMergingPlugin(),//Merge chunks
    ]
});

mix.react('resources/js/app.js', 'public/js')
   .sass('resources/sass/app.scss', 'public/css');