How to bind function references inside of a higher order function? Composition over inheritance

Question

I'm trying to create bind each function reference to a specific animal but it's never referring to the right animal I expect?

I have tried using various .call, .binds, but I am unsure how I'm misusing them.

const sleeper = animal => ({
  sleep() {
    animal.energy += 10;
    console.log(`${animal.name} is sleeping! Energy is now ${animal.energy}!`);
  }
});

const eater = animal => ({
  eat() {
    animal.energy += 5;
    console.log(`${animal.name} is eating! Energy is now ${animal.energy}!`);
  }
});

const speaker = animal => ({
  speak() {
    animal.energy -= 3;
    console.log(`${animal.name} has uttered something!`)
  }
})


const Animal = (...args) => {

  return (name, energy = 0) => {
    const animal = {
      name,
      energy,
    }

    // this is where I am confused
    const boundFunctions = args.map(func => {
      return func.bind(animal)()
    })


    return Object.assign(animal, ...boundFunctions)
  }
}

const Monkey = Animal(sleeper, eater)
const Tiger = Animal(sleeper, eater, speaker)

const Reggie = Monkey("Reggie");
const Tony = Tiger('Tony')

Reggie.sleep()
Tony.eat()

I'd like each instantiated animal to have a reference to their own name and energy. But it is undefined.

Answer 1

There's no reason to use bind here. The behavioural functions just need to be called with the animal as an argument, they return an object with a closure. Use

const boundFunctions = args.map(func => func(animal))