attempt for level 4

warrior_js_4.js

class Player {
  constructor() {
    this._health = 20
  }

  playTurn(warrior) {
    considerMovement(warrior)
  }
}

function considerMovement(warrior) {
  if (noTasksFor(warrior)) {
    evaluateSituation(warrior)
  } else {
    warrior.attack()
  }
}

function evaluateSituation(warrior) {
  if (isHealthy(warrior)) {
    warrior.walk()
  } else {
    takeSmallBreak(warrior)
  }
}

function takeSmallBreak(warrior) {
  warrior.rest()
}

function isHealthy(warrior) {
  return (warrior._health > 17)
}

function noTasksFor(warrior) {
  return warrior.feel().isEmpty()
}

function isInjured(warrior) {
  return (warrior.health() > warrior._health)
}

Be careful, the variable _health belongs to the Player class, not to the warrior instance. So you access its value by calling this._health anywhere in the class. And don't forget to update it with your current health (warrior.health()) at the end of the turn!

And you're missing this part:

you must be careful not to rest while taking damage

Good luck!