diff --git a/codes/javascript/chapter_tree/array_binary_tree.js b/codes/javascript/chapter_tree/array_binary_tree.js
index e5a5a600..92012503 100644
--- a/codes/javascript/chapter_tree/array_binary_tree.js
+++ b/codes/javascript/chapter_tree/array_binary_tree.js
@@ -40,7 +40,7 @@ class ArrayBinaryTree {
 
     /* 获取索引为 i 节点的父节点的索引 */
     parent(i) {
-        return (i - 1) / 2;
+        return Math.floor((i - 1) / 2); // 向下取整
     }
 
     /* 层序遍历 */
diff --git a/codes/typescript/chapter_tree/array_binary_tree.ts b/codes/typescript/chapter_tree/array_binary_tree.ts
index 3687bc54..a32c3a72 100644
--- a/codes/typescript/chapter_tree/array_binary_tree.ts
+++ b/codes/typescript/chapter_tree/array_binary_tree.ts
@@ -42,7 +42,7 @@ class ArrayBinaryTree {
 
     /* 获取索引为 i 节点的父节点的索引 */
     parent(i: number): number {
-        return (i - 1) / 2;
+        return Math.floor((i - 1) / 2); // 向下取整
     }
 
     /* 层序遍历 */
@@ -148,4 +148,4 @@ console.log('中序遍历为：' + res);
 res = abt.postOrder();
 console.log('后序遍历为：' + res);
 
-export {};
+export { };