Article: Composition Alone Can't Replace Inheritance - restricted inheritance

restrictedInheritance.js

const monsterHelpers = {
  attack() {
    playHurtAnimation()
  }
}

class MonsterBehaviors {
  #id = Math.random()
  #dropLoot

  constructor({ dropLoot }) {
    if (this.constructor === MonsterBehaviors) {
      throw new Error('This is an abstract class. Do not instantiate it directly.');
    }
    this.#dropLoot = dropLoot
  }

  die() {
    userInventory.add(this.#dropLoot())
    removeFromUi(this.#id)
  }
  // Other shared functions could be defined here as well.
}

export class Slime extends MonsterBehaviors { ... }

export class Skeleton extends MonsterBehaviors { ... }

export class Clown extends MonsterBehaviors {
  constructor() {
    super({
      dropLoot: () => this.dropLoot()
    })
  }

  dropLoot() {
    return [new Key()]
  }

  attack() {
    monsterHelpers.attack()
    if (itsTime()) {
      showCutScene()
    }
  }
}