tree-shaking webpack.config.js

webpack.config.js

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

module.exports = {
  entry: path.resolve(__dirname, 'src/index.js'),
  output: {
    filename: 'index.bundle.js',
    path: path.resolve(__dirname, 'build')
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: [
          {
            loader: 'babel-loader',
            options: {
              presets: [
                ["es2015", { "modules": false }] // IMPORTANT
              ]
            }
          }
        ]
      }
    ]
  }
};