webpack.config.js

const path = require('path');
const webpack = require('webpack');
const CopyWebpackPlugin = require('copy-webpack-plugin');
const { CleanWebpackPlugin } = require('clean-webpack-plugin');

module.exports = {
  mode: 'production',
  devtool: 'source-map',
  entry: {
    background: './src/background.js',
    contentScript: './src/contentScript.js',
  },
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].bundle.js',
  },
  module: {
    rules: [
      {
        test: /\.m?js$/,
        exclude: /(node_modules|bower_components)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env'],
            plugins: ['@babel/plugin-proposal-object-rest-spread'],
          },
        },
      },
    ],
  },
  plugins: [
    new CleanWebpackPlugin({
      cleanStaleWebpackAssets: false,
    }),
    new CopyWebpackPlugin({
      patterns: [
        {
          from: './src/images',
          to: './images',
        },
        {
          from: './src/manifest.json',
          to: './',
        },
      ],
    }),
    new webpack.optimize.SplitChunksPlugin(),
  ],
};