Exercise · Classes and prototypes · lesson 12 of 12

Exercise: shapes

The starter code has the finished class Shape and the beginnings of its two subclasses: Rect with the width width and the height height, and Circle with the radius radius. In Rect and Circle, complete the constructors and the area() methods, which return the area; for a circle it is Math.PI * radius * radius. Write a function function totalArea(shapes) that returns the sum of the areas of all shapes in the array. The tests create shapes with new, for example new Rect(2, 3).

new Rect(2, 3).area() → 6
new Circle(1).area() → 3.141592653589793
totalArea([new Rect(1, 1), new Rect(2, 5)]) → 11

Constraints: sizes are positive numbers; a fractional result is compared to within 0.000000001; the array may mix rectangles and circles, and for an empty array totalArea returns 0.

Do not add extra imports unless the task says so explicitly.

shapes.js — javascript

javascript · 26 lines

class Shape {}

class Rect extends Shape {
    constructor(width, height) {
        super();
    }

    area() {
        return -1;
    }
}

class Circle extends Shape {
    constructor(radius) {
        super();
    }

    area() {
        return -1;
    }
}

function totalArea(shapes) {
    return -1;
}

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