DAY 5: Inheritance

Hackerrank Solution 10 Days Of Javascript

Objective

In this challenge, we practice implementing inheritance and use JavaScript prototypes to add a new method to an existing prototype. Check out the attached Classes tutorial to refresh what we've learned about these topics.

Task

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

Add an area method to Rectangle's prototype.
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.

SOLUTION

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);
            this.h = s;
            this.w = 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);
}

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DAY 5: Inheritance | Hackerrank Solution | 10 Days Of Javascript