webpack.config.js

const path = require('path')
const ExtractTextPlugin = require('extract-text-webpack-plugin')

module.exports = {
  entry: [
    './src/index.js'
  ],
  output: {
    libraryTarget: 'umd',
    path: path.resolve(__dirname, 'dist'),
    filename: 'index.js'
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /(node_modules)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['es2015', 'stage-1']
          }
        }
      },
      {
        test: /\.css$/,
        use: ExtractTextPlugin.extract({
          fallback: 'style-loader',
          use: [
            {loader: 'css-loader'}
          ]
        })
      }
    ]
  },
  plugins: [new ExtractTextPlugin('nprogress.css')],
  externals: [{ axios: 'axios' }]
}