diff --git a/packages/core/src/flat/index.ts b/packages/core/src/flat/index.ts
index 89f39a2a..4d2fe8ee 100644
--- a/packages/core/src/flat/index.ts
+++ b/packages/core/src/flat/index.ts
@@ -1,20 +1,22 @@
 import type { Egg, EggTuple } from '@/contracts'
 
+const isArray = Array.isArray
+
 export const flat = (tuple: EggTuple): Egg[] => {
   const result: Egg[] = []
 
-  const flat = (tuple: EggTuple): void => {
+  const flatten = (tuple: EggTuple): void => {
     tuple.forEach(item => {
-      if (Array.isArray(item)) {
-        flat(item)
+      if (isArray(item)) {
+        flatten(item)
       } else {
         result.push(item)
       }
     })
   }
 
-  if (Array.isArray(tuple)) {
-    flat(tuple)
+  if (isArray(tuple)) {
+    flatten(tuple)
   }
 
   return result