Change babel-preset to cjs and update config

Author: ryanhefner

.babelrc

@@ -1,3 +1,3 @@
 {
-  "presets": ["./tools/babel-preset.js"]
+  "presets": ["./tools/babel-preset.cjs"]
 }

src/.babelrc

@@ -1,3 +1,3 @@
 {
-  "presets": [ "../tools/babel-preset" ]
+  "presets": [ "../tools/babel-preset.cjs" ]
 }

tools/babel-preset.cjs

@@ -0,0 +1,33 @@
+const BABEL_ENV = process.env.BABEL_ENV
+const building = BABEL_ENV != undefined && BABEL_ENV !== 'cjs'
+
+const plugins = [
+  '@babel/plugin-proposal-class-properties',
+  '@babel/plugin-proposal-object-rest-spread',
+  '@babel/plugin-syntax-import-assertions',
+  '@babel/plugin-transform-runtime',
+]
+
+if (process.env.NODE_ENV === 'production') {
+  plugins.push('babel-plugin-dev-expression')
+}
+
+module.exports = function () {
+  return {
+    env: {
+      test: {
+        presets: ['@babel/preset-env', '@babel/preset-react'],
+      },
+    },
+    presets: [
+      [
+        '@babel/preset-env',
+        {
+          modules: building ? false : 'commonjs',
+        },
+      ],
+      '@babel/preset-react',
+    ],
+    plugins: plugins,
+  }
+}