> For the complete documentation index, see [llms.txt](https://davin-hong3.gitbook.io/d/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://davin-hong3.gitbook.io/d/programming/hackerrank/hackerrank-10-days-javascript-challenge/day-5-inheritance.md).

# Day 5 : Inheritance

We provide the implementation for a *Rectangle* class in the editor. Perform the following tasks:

1. Add an *area* method to *Rectangle*'s prototype.
2. Create a *Square* class that satisfies the following:
   * It is a subclass of *Rectangle*.
   * It contains a constructor and no other methods.
   * It can use the *Rectangle* class' *area* method to print the area of a *Square* object.

Locked code in the editor tests the class and method implementations and prints the *area* values to STDOUT.

```javascript
class Rectangle {
    constructor(w, h) {
        this.w = w;
        this.h = h;
    }
}
// Write code that adds an 'area' method to the Rectangle class' prototype
 Rectangle.prototype.area = function () {
     return this.w*this.h;
 }
 
// Create a Square class that inherits from Rectangle and implement its class constructor
class Square extends Rectangle {
     constructor(s){
         super(s,s); //sets the values of w and h to s
         
     }
 }
 
if (JSON.stringify(Object.getOwnPropertyNames(Square.prototype)) === JSON.stringify([ 'constructor' ])) {
    const rec = new Rectangle(3, 4);
    const sqr = new Square(3);
    
    console.log(rec.area());
    console.log(sqr.area());
} else {
    console.log(-1);
    console.log(-1);
}
```