improve codebase

babel.config.base.js

@@ -1,21 +1,21 @@
 module.exports = function (api) {
   api.cache.using(() => process.env.NODE_ENV);
+  const isRollup = api.caller((caller) => !!(caller && caller.name === 'babel-rollup-build'));
+  const isJest = api.caller((caller) => !!(caller && caller.name === 'babel-jest'));
 
-  if (api.env('build')) {
+  if (isRollup) {
     return {
       plugins: ['@babel/plugin-transform-runtime', '@babel/plugin-proposal-class-properties'],
     };
   }
 
-  if (api.env('test')) {
+  if (isJest) {
     return {
       plugins: ['@babel/plugin-transform-modules-commonjs'],
       presets: [
         [
           '@babel/preset-env',
           {
-            useBuiltIns: 'usage',
-            corejs: { version: 3, proposals: true },
             targets: {
               node: 'current',
             },