SOURCE

function Ninja() {
  let _skillLevel = 0
  
  Object.defineProperty(this, "skillLevel", {
    get: () => {
    	console.log("the get method is called")
      return _skillLevel
    },
    set: value => {
      console.log("the set method is called")
      _skillLevel = value
    }
  })
}

const ninja = new Ninja()

console.log(ninja.skillLevel)

ninja.skillLevel = 100

console.log(ninja.skillLevel)