From 13bc50eb7e394e86722c2c9aba10bd2865114de1 Mon Sep 17 00:00:00 2001
From: Jaydon <jlzhao986@gmail.com>
Date: Fri, 24 Jul 2026 03:57:54 +0800
Subject: [PATCH] docs(js_notes): keep improved repeat (edge case), comment out
 old versions
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- F: user improved repeat to check times===0 BEFORE fn() so repeat(fn,0)
  prints 0 times; keep it live, comment the two earlier versions as ❌
  contrast (never leave duplicate live const → SyntaxError)
- my-mistakes M: add re-occurrence context (new version written but old
  not deleted → duplicate const)
---
 js_notes/00-concepts/my-mistakes.md |  5 ++++-
 js_notes/10-functions.js            | 17 +++++++++++++++--
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/js_notes/00-concepts/my-mistakes.md b/js_notes/00-concepts/my-mistakes.md
index 9ce9827..6d6cf81 100644
--- a/js_notes/00-concepts/my-mistakes.md
+++ b/js_notes/00-concepts/my-mistakes.md
@@ -124,12 +124,15 @@ describe: function () => {...}   // ❌ 语法错:function 和 => 不能同时
 
 ## M. const 同名声明两次
 
-📍来源:`../07-objects/practice.js` 练习 D
+📍来源:`../07-objects/practice.js` 练习 D;又见 `../10-functions.js` 练习 F
 ```js
 const student = {...}
 const student = {...} // ❌ Identifier 'student' has already been declared
 ```
 - **教训**:同作用域 `const` 不能重名;想留"错误对照"就**注释掉**旧的,别当活代码。
+- **重演情境(10章F)**:迭代改进时【新写了一版更好的 `const repeat`,却忘了删/注释掉旧版】
+  → 两个活的 `const repeat` → 整个文件直接报错跑不了。
+  改进代码时:**旧版要么删,要么注释成 ❌ 对照,绝不能两个都当活代码**。
 
 ## N. 以为"代码块能算出值、会自动返回"⭐⭐(概念推错,非手滑)
 
diff --git a/js_notes/10-functions.js b/js_notes/10-functions.js
index 7e2d408..afc6b02 100644
--- a/js_notes/10-functions.js
+++ b/js_notes/10-functions.js
@@ -251,15 +251,28 @@ console.log(triple(7))
 //   提示:times 次 → 用循环;fn 是"传进来的函数",直接 fn() 就能调用
 
 const fn = () => {console.log("执行一次fn函数")}
+
+// ❌ 最初版:把 repeat 和 fn 搞混,fn(fn, times-1) —— fn 不会递归,只执行一次
 // const repeat = (fn, times) => {
 //   if (times === 0) return
 //   return fn(fn, times -1)
 // }
+
+// ❌ 第二版:fn() 在前、判断在后 —— 能跑,但 repeat(fn, 0) 会先打印再停 = 打印 1 次(边界错)
+// const repeat = (fn, times) => {
+//   fn()
+//   times -= 1
+//   if (times === 0) return
+//   repeat(fn, times)
+// }
+
+// ✅ 终版:判断在前 → repeat(fn, 0) 直接返回,打印 0 次(边界正确)
 const repeat = (fn, times) => {
+  if (times === 0) return // 先判断:times 为 0 就不打印(edge case 处理对)
   fn()
   times-=1
-  if (times === 0) return
   // return repeat(fn, times)
-  repeat(fn, times)
+  repeat(fn, times) // 不需要 return 也行(不需要返回值)
 }
+
 repeat(fn, 3)
\ No newline at end of file