Composition over Inheritance in JS

composition.js

// Prototypal OO with ES6

// Eric Elliott's example
let animal = {
  animalType: 'animal',
  
  describe () {
    return `An ${this.animalType}, with ${this.furColor} fur, 
      ${this.legs} legs, and a ${this.tail} tail.`;
  }
};

let mouse = Object.assign(Object.create(animal), {
  animalType: 'mouse',
  furColor: 'brown',
  legs: 4,
  tail: 'long, skinny'
});

console.log(mouse.describe());


// better example with Factories
let animal = {
  animalType: 'animal',
 
  describe () {
    return `An ${this.animalType} with ${this.furColor} fur, 
      ${this.legs} legs, and a ${this.tail} tail.`;
  }
};
 
let mouseFactory = function mouseFactory () {
  let secret = 'secret agent';

  return Object.assign(Object.create(animal), {
    animalType: 'mouse',
    furColor: 'brown',
    legs: 4,
    tail: 'long, skinny',
    profession () {
      return secret;
    }
  });
};
 
let james = mouseFactory();