brunch-config.js

exports.config = {
  optimize: false,
  sourceMaps: true,

  files: {
    javascripts: {
      joinTo: "js/app.dev.js"
    },
    stylesheets: {
      joinTo: "css/app.dev.css",
    },
  },

  conventions: {
    // This option sets where we should place non-css and non-js assets in.
    assets: /^(web\/static\/assets)/
  },

  // Phoenix paths configuration
  paths: {
    // Dependencies and current project directories to watch
    watched: [
      "deps/phoenix/web/static",
      "deps/phoenix_html/web/static",
      "web/static",
      "test/static"
    ],

    // Where to compile files to
    public: "priv/static"
  },

  // Configure your plugins
  plugins: {
    babel: {
      presets: ['react', 'es2015'],
      // Do not use ES6 compiler in vendor code
      ignore: [/web\/static\/vendor/]
    },
    sass: {
      mode: 'native' // Use libsass. Change to 'ruby' to use the gem
    },
    uglify: {
      mangle: false,
      compress: false,
    }
  },

  modules: {
    autoRequire: {
      "js/app.dev.js": ["web/static/js/app"]
    }
  },

  // Production settings
  overrides: {
    production: {
      optimize: true,
      sourceMaps: false,
      plugins: {
        uglify: {
          compress: true,
          mangle: true
        }
      },
      files: {
        javascripts: {
          joinTo: "js/app.prod.js"
        },
        stylesheets: {
          joinTo: "css/app.prod.css",
        },
      },
      modules: {
        autoRequire: {
          "js/app.prod.js": ["web/static/js/app"]
        }
      },
    },
  },

  npm: {
    enabled: true
  }
};

package.json

{
  "name": "",
  "version": "1.0.0",
  "description": "",
  "directories": {
    "test": "test"
  },
  "repository": {},
  "scripts": {
    "build": "brunch build",
    "prod": "brunch build --production",
    "watch": "brunch watch",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Andrea Pavoni",
  "license": "",
  "dependencies": {
    "react": "^0.14.6",
    "react-dom": "^0.14.6"
  },
  "devDependencies": {
    "babel-brunch": "^6.0.0",
    "babel-core": "^6.4.0",
    "babel-preset-es2015": "^6.3.13",
    "babel-preset-react": "^6.3.13",
    "brunch": "^2.0.0",
    "javascript-brunch": ">= 1.0 < 1.8",
    "sass-brunch": "^1.9.2",
    "uglify-js-brunch": ">= 1.0 < 1.8"
  }
}