Simple PIN validation

Question

Task: ATM machines allow 4 or 6 digit PIN codes and PIN codes cannot contain anything but exactly 4 digits or exactly 6 digits. If the function is passed a valid PIN string, return true, else return false.

My solution:

function validatePIN (pin) {
  //return true or false
  if (!isNaN(pin) && Number.isInteger(pin) && pin.toString().length == 4 || pin.toString().length == 6) { 
    return true 
  } else { 
    return false 
  }
}

The only bug I get is when I pass 4 digits as a string ("1234") - it equals false.

Answer 1

function validatePIN (pin) {
  return typeof pin === 'string' && // verify that the pin is a string
    Number.isInteger(+pin) && // make sure that the string is an integer when converted into a number
    [4, 6].includes(pin.length) // only accepts 4 and 6 character pins
}