Daily Challenge #292 - ISBN-10 Identifiers

const validISBN10 = (num) => { 
  if (!/[0-9]{9}[X0-9]{1}/.test(num)) return false;
  return (num.split('').map((d, i) => d === 'X' ? (10 * (i + 1)) : (d * (i + 1))).reduce((a, b) => a + b) % 11 === 0)
}

public static boolean validISBN10(String s){
        int sum = 0;
        if(s.matches("[0-9]{9}[X0-9]{1}"))
        {
            for(int i = 0; i < s.length(); i++) {
                sum += s.charAt(i) == 'X' ? 10 * (i + 1) : Character.getNumericValue(s.charAt(i)) * (i + 1);
            }
            if(sum % 11 == 0) return true;
        }
        return false;
    }

function validISBN10(isbn) {
  let index = 0;
  let checkSum = 0;
  let xCount = 0;
  for (; index < isbn.length; index++) {
    if (isbn[index] === 'X') {
      xCount += 1;
    }
    checkSum += parseInt(isbn[index]) * (index+1);
  }

  if (isbn.length !== 10) {
    return false;
  }

  if (isbn[isbn.length-1] === 'X' && xCount === 1) {
    return true;
  }

  return checkSum % 11 === 0;
}