Grammar correction (yangshun#31)

Correcting full stop typo to comma.

front-end/interview-questions.md

@@ -621,7 +621,7 @@ For an in-depth explanation, do check out his [article on Medium](https://codebu
 
 ### Explain how prototypal inheritance works
 
-This is an extremely common JavaScript interview question. All JavaScript objects have a `prototype` property, that is a reference to another object. When a property is accessed on an object and if the property is not found on that object, the JavaScript engine looks at the object's `prototype`. and the `prototype`'s `prototype` and so on, until it finds the property defined on one of the `prototype`s or until it reaches the end of the prototype chain. This behaviour simulates classical inheritance, but it is really more of [delegation than inheritance](https://davidwalsh.name/javascript-objects).
+This is an extremely common JavaScript interview question. All JavaScript objects have a `prototype` property, that is a reference to another object. When a property is accessed on an object and if the property is not found on that object, the JavaScript engine looks at the object's `prototype`, and the `prototype`'s `prototype` and so on, until it finds the property defined on one of the `prototype`s or until it reaches the end of the prototype chain. This behaviour simulates classical inheritance, but it is really more of [delegation than inheritance](https://davidwalsh.name/javascript-objects).
 
 ###### References