Webpack config file for local Wordpress plugin development with more minification and backwards compatibility for more extensive testing.

webpack.config.test.js

/**
 * Dev Webpack mode for cross-browser fixing
 * Uses regular Webpack not Webpack-server.
 * Uses BrowserSync to create a local server.
 * Watch mode compiles and reloads on changes.
 * Slower, css and js minification version.
 */

const path = require('path')
const webpack = require('webpack')
const BrowserSyncPlugin = require('browser-sync-webpack-plugin')
const { CleanWebpackPlugin } = require('clean-webpack-plugin')
const MiniCssExtractPlugin = require("mini-css-extract-plugin")
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin")
const TerserPlugin = require('terser-webpack-plugin')
const postcss = require('postcss')
const postcssPresetEnv = require('postcss-preset-env')
const CopyPlugin = require('copy-webpack-plugin')

module.exports = {
  mode: 'development',
  entry: {
    myApp_admin: "./src/scss/admin_styles.scss",
		myApp:  [ "./src/index.js" ],
  },
  output: {
    filename: 'js/[name].js',
    path: path.resolve(__dirname, 'assets')
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env'],
          }
        }
      },
      {
        test: /\.s[c|a]ss$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader',
          {
            loader: 'postcss-loader',
            options: {
              ident: 'postcss',
              plugins: [
                require('postcss-preset-env')
              ]
            }
          },
          'sass-loader'
        ]
      }
    ]
  },
  plugins: [
    new webpack.ProgressPlugin(),
    new CleanWebpackPlugin(),
    new MiniCssExtractPlugin({
      filename: 'css/[name].css'
    }),
    new CopyPlugin([
      {
        from: 'img/**/*',
        to: 'img/[name].[ext]',
        context: 'src/'
        // dot: true,
        // toType: 'dir',
      }
    ]),
    new BrowserSyncPlugin(
      // BrowserSync options
      {
        files: '**/*.php',
        // browse to http://localhost:3000/ during development
        host: 'localhost',
        port: 3000,
        proxy: 'http://yourlocalserver.dev/',
      },
      // plugin options
      {
        // reload: true,
        // injectCss: true, // doesn't work
        injectChanges: true
      }
    )
  ],
  optimization: {
    minimizer: [
      new OptimizeCSSAssetsPlugin({
        cssProcessorOptions: {
          discardComments: true,
          map: {
            inline: false,
            annotation: true
          },
          safe: true
        },
      }),
      new TerserPlugin({
        parallel: true,
        terserOptions: {
          safari10: true
        }
      })
    ]
  }
}