crypto_animal_decorator.js

// CryptoAnimal - interface we're extending with concrete instances and decorators
class CryptoAnimal {
  // each animal has some sort of history that makes them who they are today
  background() {
    throw new Error('implement me pls');
  }

  // all of the things in that history make them less common
  rarity() {
    throw new Error('implement me pls');
  }

  // useful trinkets picked up along the way
  talismans() {
    throw new Error('implement me pls');
  }
}

// CryptoKitty - concrete CryptoAnimal class, used as a base to build from with decorators
class CryptoKitty extends CryptoAnimal {
  background() {
    return ['Born a kitty'];
  }

  rarity() {
    return 0.5;
  }

  talismans() {
    return [];
  }
}

// CryptoDoggo - concrete CryptoAnimal class, used as a base to build from with decorators
class CryptoDoggo extends CryptoAnimal {
  background() {
    return ['Born a doggo'];
  }

  rarity() {
    return 0.4;
  }

  talismans() {
    return ['Old tattered copy of "All Dogs Go To Heaven"'];
  }
}

// Decorator class - used to define variants of our crypto animals
class CryptoDecorator extends CryptoAnimal {
  constructor(animal) {
    super();
    this.animal = animal;
  }
}

/*
  The remaining classes are all decorations
  These can be inifinite, they just have to extend the CryptoDecorator class
*/

class Ninja extends CryptoDecorator {
  background() {
    return [...this.animal.background(), 'Went to Ninja school'];
  }

  rarity() {
    return this.animal.rarity() * 0.3;
  }

  talismans() {
    return [...this.animal.talismans(), 'Sweet ninja star'];
  }
}

class Samurai extends CryptoDecorator {
  background() {
    return [...this.animal.background(), 'Trained as a Samurai'];
  }

  rarity() {
    return this.animal.rarity() * 0.05;
  }

  talismans() {
    return this.animal.talismans();
  }
}

class BookStudent extends CryptoDecorator {
  background() {
    return [...this.animal.background(), 'Studied the "Way of the Book"'];
  }

  rarity() {
    return this.animal.rarity() * 0.15;
  }

  talismans() {
    return [...this.animal.talismans(), 'University brochure titled "The Way of the Book"'];
  }
}

class Bespectacled extends CryptoDecorator {
  background() {
    return [...this.animal.background(), 'Lost sharpness of vision, and picked up "Glasses of Fortitude"'];
  }

  rarity() {
    return this.animal.rarity() * 0.15;
  }

  talismans() {
    return [...this.animal.talismans(), 'Glasses of Fortitude'];
  }
}

class Hippie extends CryptoDecorator {
  background() {
    return [...this.animal.background(), 'Went to Woodstock'];
  }

  rarity() {
    return this.animal.rarity() * 0.45;
  }

  talismans() {
    return [...this.animal.talismans(), 'Hash pipe'];
  }
}

function run() {
  const guy1 = new Bespectacled(new BookStudent(new Samurai(new CryptoDoggo())));
  const guy2 = new Hippie(new Ninja(new CryptoKitty()));

  console.log('guy 1:');
  console.log('BACKGROUND:', guy1.background());
  console.log('RARITY:', guy1.rarity());
  console.log('TALISMANS:', guy1.talismans());

  console.log('\n');

  console.log('guy 2:');
  console.log('BACKGROUND:', guy2.background());
  console.log('RARITY:', guy2.rarity());
  console.log('TALISMANS:', guy2.talismans());
}

run();

guy 1:
BACKGROUND: [
  'Born a doggo',
  'Trained as a Samurai',
  'Studied the "Way of the Book"',
  'Lost sharpness of vision, and picked up "Glasses of Fortitude"'
]
RARITY: 0.00045000000000000004
TALISMANS: [
  'Old tattered copy of "All Dogs Go To Heaven"',
  'University brochure titled "The Way of the Book"',
  'Glasses of Fortitude'
]


guy 2:
BACKGROUND: [
   'Born a kitty',
  'Went to Ninja school',
  'Went to Woodstock'
]
RARITY: 0.0675
TALISMANS: [
  'Sweet ninja star',
  'Hash pipe'
]