hkid-validation.js

hkid-validation.js

function charToNumber(char) {
  if (char === ' ') {
      return 58
  } else if (!isNaN(char)) {
      return parseInt(char)
  } else {
      return char.toUpperCase().charCodeAt(0) - 55;
  }
}

function hkidValidator(input) {
  if(!input) return false;
  if(typeof input !== 'string') return false;

  const inputLength = input.length;
  if (inputLength < 8 || inputLength > 9) return false;

  let hkid = input;
  if (inputLength === 8) {
      hkid = ' ' + hkid;
  }

  console.assert(hkid.length === 9);

  const lastChar = hkid[hkid.length - 1];
  if (charToNumber(lastChar) >= 11) return false;

  let total = hkid.split('')
    .map(c => charToNumber(c))
    .reduce((acc, curr, i) => acc + (hkid.length - i) * curr, 0);

  if(total % 11 !== 0) return false;

  return true;
}