diff --git a/hello/app.js b/hello/app.js
index 7fe3c0a..d1d62cd 100644
--- a/hello/app.js
+++ b/hello/app.js
@@ -3,8 +3,7 @@
 let bookId = 0;
 
 function genNewBookId() {
-    bookID = 1;
-    bookID++;
+    bookId++;
     return bookId;
 }