Merge pull request #2021 from lumosmind/patch-44

to make binding more clear

1-js/06-advanced-functions/10-bind/article.md

@@ -167,7 +167,7 @@ sayHi(); // Hello, John!
 setTimeout(sayHi, 1000); // Hello, John!
 
 // even if the value of user changes within 1 second
-// sayHi uses the pre-bound value
+// sayHi uses the pre-bound value which is reference to the old user object
 user = {
   sayHi() { alert("Another user in setTimeout!"); }
 };