$ mkdir my-frontend
$ cd my-frontend
$ git init
$ npm init

$ echo 'node_modules' >> .gitignore
$ git add .gitignore
$ git commit -m 'Add "node_modules" to .gitignore'

$ git add package.json
$ git commit -m 'Add bare "package.json" (npm init)'

$ mkdir build
$ echo 'hello world' >> build/index.html

$ npm i -s webpack
  # same as: npm install --save webpack

$ npm i -D webpack-dev-server
  # same as: npm install webpack-dev-server --save-dev

Add the lines starting with "dev" and "build" (lines 2 and 3) to package.json:

// package.json
"scripts": {
  "dev": "webpack-dev-server --devtool eval --progress --colors --content-base build",
  "build": "webpack",
  "test": "echo \"Error: no test specified\" && exit 1"
},

Let’s check the result:

$ npm run dev

$ curl http://localhost:8080
  # => hello world

$ google-chrome http://localhost:8080/webpack-dev-server/
  # => "Connecting to socket.io server..."

Let’s add the minimum dependencies needed for developing with React, using .jsx on Webpack:

$ npm i -s babel-core babel-loader react

Let’s start with a basic configuration in webpack.config.js

// webpack.config.js
'use strict';

var webpack = require('webpack');

module.exports = {
  entry: [
    './app/main.jsx'
  ],
  resolve: {
    extensions: ['', '.js', '.jsx'],
    modulesDirectories: ['node_modules', 'app']
  },
  output: {
    path:     './build',
    filename: 'bundle.js'
  },
  module: {
    loaders: [
      {
        test: /\.jsx$/,
        exclude: /(node_modules)/,
        loader: 'babel-loader'
      }
    ]
  }
};

Let’s add a basic app/main.jsx to make sure it’s working:

// app/main.jsx 
console.log("hello from app/main.jsx !!");

And let’s run webpack:

$ npm run build

And check the result:

$ ls build
  # => bundle.js  index.html

Now if you run a:

$ cat buils/bundle.js

Then, at the end of the output, you should see something like this:

/***/ },
/* 1 */
/***/ function(module, exports) {

  "use strict";

  console.log("hello from app/main.jsx !!");

/***/ }
/******/ ]);%

Which means Webpack recognised your source app/main.jsx and bundled it coorectly.