Fix a typo

Author: zhang1pr

1-js/09-classes/02-class-inheritance/article.md

@@ -438,7 +438,7 @@ It works as intended, due to `[[HomeObject]]` mechanics. A method, such as `long
 
 As we've known before, generally functions are "free", not bound to objects in JavaScript. So they can be copied between objects and called with another `this`.
 
-The very existance of `[[HomeObject]]` violates that principle, because methods remember their objects. `[[HomeObject]]` can't be changed, so this bond is forever.
+The very existence of `[[HomeObject]]` violates that principle, because methods remember their objects. `[[HomeObject]]` can't be changed, so this bond is forever.
 
 The only place in the language where `[[HomeObject]]` is used -- is `super`. So, if a method does not use `super`, then we can still consider it free and copy between objects. But with `super` things may go wrong.