Prototypes and Inheritance

Question 1

How does JavaScript handle prototype method shadowing?

Answer 1

If an object has a method with the same name as a prototype method, JavaScript uses the object’s own method first. Deleting the instance method allows the prototype method to be used again.

Question 2

Can you modify the prototype of built-in objects like Array?

Answer 2

Yes, but it is not recommended because it can lead to unexpected behavior and break other code.

Example: Array.prototype.last = function() { return this[this.length - 1]; }; console.log([1, 2, 3].last()); // 3

Question 3

What will be the output of the following code: function A() {} A.prototype.x = 10; let obj = new A(); obj.x = 20; delete obj.x; console.log(obj.x);?

Answer 3

10

obj.x = 20 creates an instance property, shadowing the prototype. delete obj.x removes the instance property, so JavaScript falls back to A.prototype.x.