webpack.config.dev.js

const merge = require('webpack-merge');
const webpack = require('webpack');
const common = require('./webpack.config');

module.exports = merge(common, {
  devtool: 'source-map',
  mode: 'development',
  devServer: {
    contentBase: './dist',
    port: 9000,
    headers: {
      'Access-Control-Allow-Origin': '*'
    }
  },
  plugins: [
    new webpack.NamedModulesPlugin(),
    new webpack.HotModuleReplacementPlugin()
  ],
  module: {
    rules: [
      {
        test: /\.m?js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env']
          }
        }
      }
    ]
  }
});