webpack.config.js

const path = require('path')
const webpack = require('webpack')

module.exports = {
    context: path.resolve(__dirname, './src'),
    entry: {
        app: './js/index.js',
    },
    output: {
        path: path.resolve(__dirname, './dist'),
        publicPath: '/dist/',
        filename: 'bundle.js'
    },
    devtool: '#eval-source-map',
    module: {
        rules: [{
            test: /\.js$/,
            loader: 'babel-loader',
            exclude: /node_modules/,
            query: {
              presets: ['es2015']
            }
        },
        {
            test: /\.css$/,
            use: ['style-loader','css-loader']
        }]
    }
}

if (process.env.NODE_ENV === 'production') {
  module.exports.devtool = '#source-map'
  module.exports.plugins = (module.exports.plugins || []).concat([
    new webpack.DefinePlugin({
      'process.env': {
        NODE_ENV: '"production"'
      }
    }),
    new webpack.optimize.UglifyJsPlugin({
      sourceMap: true,
      compress: {
        warnings: false
      }
    }),
    new webpack.LoaderOptionsPlugin({
      minimize: true
    })
  ])
}