Dynamic dispatch

dynamic_dispatch.js

const handleShape = (shape) => { console.log(shape.area()); }

class Shape
{
    constructor(width = 2)
    {
        this.width = width;
    }
    area()
    {
         return 0;
    }
}

class Square extends Shape
{ 
    area()
    {
        return this.width ** 2;  
    }
}

class Circle extends Shape
{
    area()
    {
        return Math.PI * (this.width / 2) ** 2;
    }
}

const shape = new Square();

handleShape(shape);    // logs 4