javascript: Function composition

//Function composition
function Animal(name) {
    let publicAPI = {
        say: function() {
            console.log(`I am ${name}`);
        }
    }

    return publicAPI
}

function Rabbit(name) {
    let animalPublicAPI = new Animal(name)

    let publicAPI = {
        skip: function() {
            console.log(name + ': I skip');
        }
    }

    return Object.assign(publicAPI, animalPublicAPI)
}

let r1 = Rabbit('r1')
r1.say()
r1.skip()