From 15748e871ea7e12906e7c5ace8aabc2f5f5efa95 Mon Sep 17 00:00:00 2001
From: KaiYu Feng <loveress01@outlook.com>
Date: Fri, 1 May 2020 00:14:45 +0800
Subject: [PATCH] fix(docs/mapping-types): fix wrong demo code.

get index before push, so the access of this index won't beyond the boundery.
---
 docs/types/mapping-types.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/types/mapping-types.rst b/docs/types/mapping-types.rst
index f69d25b0f..d84da8ec5 100644
--- a/docs/types/mapping-types.rst
+++ b/docs/types/mapping-types.rst
@@ -138,8 +138,8 @@ the ``sum`` function iterates over to sum all the values.
             if (keyIndex > 0)
                 return true;
             else {
-                self.keys.push();
                 keyIndex = self.keys.length;
+                self.keys.push();
                 self.data[key].keyIndex = keyIndex + 1;
                 self.keys[keyIndex].key = key;
                 self.size++;