Feat code splitting

.eslintrc

@@ -0,0 +1,11 @@
+{
+  "parser": "babel-eslint",
+  "parserOptions": {
+    "babelOptions": {
+      "presets": [
+        ["babel-preset-react-app", false],
+        "babel-preset-react-app/prod"
+      ]
+    }
+  }
+}

getFiles.js

@@ -0,0 +1,28 @@
+/* eslint-disable import/prefer-default-export */
+const fs = require('fs');
+
+export const getFiles = (entry, extensions = [], excludeExtensions = []) => {
+  let fileNames = [];
+  const dirs = fs.readdirSync(entry);
+
+  dirs.forEach((dir) => {
+    const path = `${entry}/${dir}`;
+
+    if (fs.lstatSync(path).isDirectory()) {
+      fileNames = [
+        ...fileNames,
+        ...getFiles(path, extensions, excludeExtensions),
+      ];
+
+      return;
+    }
+
+    if (!excludeExtensions.some((exclude) => dir.endsWith(exclude))
+      && extensions.some((ext) => dir.endsWith(ext))
+    ) {
+      fileNames.push(path);
+    }
+  });
+
+  return fileNames;
+};