Functional JS approach to classic Animals OO example - https://jsfiddle.net/wjkLagf8/1/

animals.js

const animal = {
    type: 'animal',
    talk() {
        alert('Hello, world!');
    },
    move() {
        alert(`${this.name} the ${this.type} moved forward`);
    }
};

const createAnimal = (name = 'george') =>
    Object.assign(Object.create(animal), {
        name
    });

const cow = Object.assign(createAnimal(), {
    type: 'cow',
    talk() {
        alert('moooooo');
    }
});

const createCow = (name = 'frank') =>
    Object.assign(Object.create(cow), {
        name
    });

const dog = Object.assign(createAnimal(), {
    type: 'dog',
    talk() {
        alert('woof woof');
    }
});

const createDog = (name = 'bobby') =>
    Object.assign(Object.create(dog), {
        name
    });

const jason = createAnimal('jason');
const mary = createCow('mary');
const justin = createDog('justin');

jason.talk();
mary.talk();
justin.talk();
jason.move();
mary.move();
justin.move();