es6 patterns

factory.js

class Shape {
    constructor (type, ...args) {
        super();
        switch (type) {
        case 'rect':
            return new Rectangle(...args);
        case 'circle':
            return new Circle(...args);
        }
    }
}

class Circle extends Shape {
    constructor (radius) {
        this.radius = radius;
    }
    surface () {
        return Math.PI * this.radius ** 2;
    }
}

class Rect extends Shape {
    constructor (width, height) {
        this.width = width;
        this.height = height;
    }
    surface () {
        return this.width * this.height;
    }
}
// factory method (Static Factory)
Shape.create('circle', [4]);

// abstract factory
new Shape.CircleFactory().create(4);
new Shape.RectFactory().create(5, 3);

new Shape('circle', 4);
new Shape('rect', 5, 3);