elzero_web_school_challenge.js

console.log('challenge accepted');

let x = {
  // save the real value
  _value: 0,
  // get the value implicity when needed
  valueOf: function getX() {
    return (x._value += 5);
  }
}

// while x is object it's not comparable to a number, so a (valueOf) function is exuectued(if it is defined)
if (x == 5 && x == 10 && x == 15) {
  console.log('Challenge Solved');
}

// take care for subsequent x values
if(x == 20){
  console.log('yes, x keeps incrementing forever whenever js implicity request its value');
}

// x = {"_value":20} no matter how many you print x this way
// because it trigger (toString) and not (valueOf)
console.log('x =', JSON.stringify(x));
console.log('x =', JSON.stringify(x));
console.log('x =', JSON.stringify(x));