playing with object and function composition

a_shaggy_dog_tale.js

const series = (...fns) => (...args) => fns.map(f => f(...args));

const tailFactory = (width) => {
    let wag_to_width_ratio = Math.random();
    let wagspeed = Math.ceil(width * wag_to_width_ratio);
    return {
        setWagSpeed({ width = 0 } = {}) {
            wagspeed = Math.ceil(width * wag_to_width_ratio);
        },
	wag() { console.log(Array(wagspeed).fill('WAG', 0, wagspeed).join(',')); }
    };
};

const truthFactory = () => ({
    truth() { console.log(`A ${this.roar? 'spiky' : 'shaggy'} ${this.type || 'mystery'} ${this.tail? 'tail' : ''}`); }
});

const dogFactory = (name, width, height) => {
    let w = width, o = height;
    return {
        woof() { console.log(`${name} says W${Array(w).fill('w', 0, w).join('')}${Array(o).fill('o', 0, o).join('')}of!`); },
        resizeWoof({ width = 0, height = 0 } = {}) {
            w = width, 
            o = height;
        },
        get type() { return 'dog'; }
    }
};

const dragonFactory = (name, width, height) => {
    let o = width, a = height;
    return {
        roar() { console.log(`${name} says R${Array(o).fill('o', 0, o).join('')}${Array(a).fill('a', 0, a).join('')}r!`); },
        resizeRoar({ width = 0, height = 0 } = {}) {
	    o = width,
	    a = height;
	},
        get type() { return 'dragon'; }
    }
};

const dogDragonWithATailFactory = ({ 
    name = 'fluffy', 
    w = Math.round(Math.random() * 70), 
    h = Math.round(Math.random() * 90), 
    has_a_tail = Math.random() < 0.5, 
    is_secretly_a_dragon = Math.random() > 0.5 
} = {}) => ({
    ...dogFactory(name, w, h),
    ...(is_secretly_a_dragon) && dragonFactory(name, w, h),
    ...(has_a_tail) && { tail: tailFactory(w) },
    ...truthFactory()
});

const kennelFactory = () => {
    let dogs = [];
    return {
	addDog : d => dogs.push(d),
        resize : ({ width = Math.round(Math.random() * 70), height = Math.round(Math.random() * 90) } = {}) => {
	    dogs.forEach(d => {
                series(...[d.resizeWoof, d.resizeRoar, d.tail? d.tail.setWagSpeed : undefined].filter(fn => typeof fn !== 'undefined'))({ width, height });
                series(...[d.truth.bind(d), d.woof, d.roar, d.tail? d.tail.wag : undefined].filter(fn => typeof fn !== 'undefined'))();
	    });
	    return 'Kennel Resized!';
	}
    };
};
			 
myKennel = kennelFactory();
for(let i = (Math.random() * 20); i > 0; i--) { myKennel.addDog(dogDragonWithATailFactory()); }
myKennel.resize();