title: Why do we need to use import 'babel-polyfill'; in react components?
body: <p>I wonder if we user babel loader + all the presets, why do we need to include babel-polyfill anyway into our components? I just think that babel-loader should do all the job itself.</p>
  
  <p>Examples were taken here <a href="https://github.com/reactjs/redux/tree/master/examples" rel="noreferrer">https://github.com/reactjs/redux/tree/master/examples</a></p>
  
  <p>What i am asking about is:</p>
  
  <pre><code>import 'babel-polyfill';
  import React from 'react';
  import { render } from 'react-dom';
  import App from './containers/App';
  </code></pre>
  
  <p>Here is package example:</p>
  
  <pre><code>{
    "name": "redux-shopping-cart-example",
    "version": "0.0.0",
    "description": "Redux shopping-cart example",
    "scripts": {
      "start": "node server.js",
      "test": "cross-env NODE_ENV=test mocha --recursive --compilers js:babel-register",
      "test:watch": "npm test -- --watch"
    },
    "repository": {
      "type": "git",
      "url": "https://github.com/reactjs/redux.git"
    },
    "license": "MIT",
    "bugs": {
      "url": "https://github.com/reactjs/redux/issues"
    },
    "homepage": "http://redux.js.org",
    "dependencies": {
      "babel-polyfill": "^6.3.14",
      "react": "^0.14.7",
      "react-dom": "^0.14.7",
      "react-redux": "^4.2.1",
      "redux": "^3.2.1",
      "redux-thunk": "^1.0.3"
    },
    "devDependencies": {
      "babel-core": "^6.3.15",
      "babel-loader": "^6.2.0",
      "babel-preset-es2015": "^6.3.13",
      "babel-preset-react": "^6.3.13",
      "babel-preset-react-hmre": "^1.1.1",
      "cross-env": "^1.0.7",
      "enzyme": "^2.0.0",
      "express": "^4.13.3",
      "json-loader": "^0.5.3",
      "react-addons-test-utils": "^0.14.7",
      "redux-logger": "^2.0.1",
      "mocha": "^2.2.5",
      "node-libs-browser": "^0.5.2",
      "webpack": "^1.9.11",
      "webpack-dev-middleware": "^1.2.0",
      "webpack-hot-middleware": "^2.9.1"
    }
  }
  </code></pre>
  
  <p>Here is webpack config example taken from <a href="https://github.com/reactjs/redux/tree/master/examples" rel="noreferrer">https://github.com/reactjs/redux/tree/master/examples</a></p>
  
  <pre><code>var path = require('path')
  var webpack = require('webpack')
  
  module.exports = {
    devtool: 'cheap-module-eval-source-map',
    entry: [
      'webpack-hot-middleware/client',
      './index'
    ],
    output: {
      path: path.join(__dirname, 'dist'),
      filename: 'bundle.js',
      publicPath: '/static/'
    },
    plugins: [
      new webpack.optimize.OccurenceOrderPlugin(),
      new webpack.HotModuleReplacementPlugin()
    ],
    module: {
      loaders: [
        {
          test: /\.js$/,
          loaders: [ 'babel?presets[]=react,presets[]=es2015,presets[]=react-hmre' ],
          exclude: /node_modules/,
          include: __dirname
        },
        {
          test: /\.json$/,
          loaders: [ 'json' ],
          exclude: /node_modules/,
          include: __dirname
        }
      ]
    }
  }
  </code></pre>