Getter/Setter methods in JS

class-getter-setter.js

class NinjaCollection {
  constructor() {
    this.ninjas = ['Yoshi', 'Kuma', 'Hattori'];
  }
  get firstNinja() {
    console.log('Getting firstNinja');
    return this.ninjas[0];
  }
  set firstNinja(value) {
    console.log('Setting firstNinja');
    this.ninjas[0] = value;
  }
}

const ninjaCollection = new NinjaCollection();

console.log(ninjaCollection.firstNinja === 'Yoshi', 'Yoshi is the first ninja');

ninjaCollection.firstNinja = 'Hachi';

console.log(
  ninjaCollection.firstNinja === 'Hachi' && ninjaCollection.ninjas[0] === 'Hachi',
  'Now Hachi is the first ninja'
);

new-getter-setter.js

const ninjaCollection = {
  ninjas: ['Yoshi', 'Kuma', 'Hattori'],
  get firstNinja() {
    console.log('Getting firstNinja');
    return this.ninjas[0];
  },
  set firstNinja(value) {
    console.log('Setting firstNinja');
    this.ninjas[0] = value;
  }
};

console.log(ninjaCollection.firstNinja === 'Yoshi', 'Yoshi is the first ninja');

ninjaCollection.firstNinja = 'Hachi';

console.log(
  ninjaCollection.firstNinja === 'Hachi' && ninjaCollection.ninjas[0] === 'Hachi',
  'Now Hachi is the first ninja'
);

original-getter-setter.js

function Ninja() {
  let skillLevel;

  this.getSkillLevel = () => skillLevel;

  this.setSkillLevel = (value) => {
    skillLevel = value;
  };
}

const ninja = new Ninja();
ninja.setSkillLevel(100);
console.log(ninja.getSkillLevel() === 100, 'Our ninja is at level 100!');
console.log(ninja.skillLevel === undefined, 'And we don\'t have access for the skillLevel variable');