getting there

.webpack/webpack.config.babel.js

@@ -0,0 +1,45 @@
+import { merge, mergeWithCustomize, customizeObject } from 'webpack-merge';
+import nodeExternals from 'webpack-node-externals';
+import baseConfig from './webpack.config.base';
+
+export default (_env, args) => {
+  switch (args.mode) {
+    case 'development':
+      return [
+        baseConfig,
+        merge(baseConfig, {
+          externals: [nodeExternals()],
+          output: {
+            filename: '[name].core.js',
+          },
+        }),
+      ];
+    case 'production':
+      return [
+        // umd
+        merge(baseConfig, {
+          output: {
+            filename: '[name].min.js',
+          },
+        }),
+        // esm
+        mergeWithCustomize({
+          customizeObject: customizeObject({
+            'output.library': 'replace',
+          }),
+        })(baseConfig, {
+          experiments: {
+            outputModule: true,
+          },
+          output: {
+            library: {
+              type: 'module',
+            },
+            filename: '[name].esm.min.mjs',
+          },
+        }),
+      ];
+    default:
+      throw new Error('No matching configuration was found!');
+  }
+};