Regex validate PIN Codewars-CodePudding

For this Codewars challenge, I cannot understand why the logic is not working. I've found other solutions, but would like to understand why this is not working:

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.

function validatePIN (pin) {
  
  const splitPin = pin.toString().split('')
  const finalArr = [];
  
for (let i = 0; i < splitPin.length; i  ){
  
  if (!Number.isInteger(pin[i])){
    return false;
  } else if (Number.isInteger(pin[i])){
    finalArr.push(pin[i]);
  }
}
  if(finalArr.length === 4 || finalArr.length === 6){
    console.log(finalArr.length)
    return true;
  } 
  
}

CodePudding user response：

There are some double checks that you don't need to do but you are doing because you're not sure what you're expecting.

Like the type for pin.

const splitPin = pin.toString().split('') works either way for a string or number value, because you are expecting a string, the call to .toString is unneccesary

But also that you're using Number.isInteger - this function will only return true if the function is of type integer.

But since pin is a string and splitting it returns an array of strings, the Number.isInteger call will always return false.

Try using parseInt instead. Then check for parseInt(pin[0]) !== NaN.

You can streamline the function from:

function validatePIN (pin) {
  
  const splitPin = pin.toString().split('')
  const finalArr = [];
  
for (let i = 0; i < splitPin.length; i  ){
  
  if (!Number.isInteger(pin[i])){
    return false;
  } else if (Number.isInteger(pin[i])){
    finalArr.push(pin[i]);
  }
}
  if(finalArr.length === 4 || finalArr.length === 6){
    console.log(finalArr.length)
    return true;
  } 
  
}

to something cleaner:

function validatePIN (pin) {
  const acceptedLengths = [4, 6]
  const splitPin = pin.toString().split('')
  const finalArr = [];
  
  for (let i = 0; i < splitPin.length; i  ){
    // You don't need to do an else, since you're only
    // checking for one condition.
    // just return directly
    if (parseInt(pin[i]) !== NaN){
      finalArr.push(pin[i]);
    }

    return
  }
  
  return acceptedLengths.includes(finalArr.length)
}

or even something like this:

function validatePIN(pin) {
  // Set a variable for the accepted length
  const acceptedPINLength = [4, 6];

  // If we have to check if a value in pin is an integer or not
  // then the pin variable is a string and can't be a number.
  // So skip the .toString and just split it directly.
  const numbersArray = pin.split('')
    .filter((entry) => parseInt(entry) !== NaN)
    .join('');

  // if strength is 4 or 6, return true, else false
  return acceptedPINLength.includes(numbersArray.length)
}

CodePudding user response：

I would say: no loop required at all, you don't have to filter any characters:

function validatePIN2(pin) {
  const acceptedPINLength = [4, 6];
  return acceptedPINLength.includes(pin.length()) && !isNaN(pin);
}

(Thanks to @Amats for the elegant solution with the acceptedPINLength.)