hexToDec.js

/**
 * 
 * @param {string} number 
 * @return {number} 
 */
function hexToDec(number) {
  // Return error if number is not hexadecimal or contains more than ten characters (10 digits)
  if (!/^[0-9A-Fa-f]{1,10}$/.test(number)) {
    return NaN;
  }

  // Convert hexadecimal number to decimal
  const decimal = parseInt(number, 16);

  // Return decimal number
  return (decimal >= 549755813888) ? decimal - 1099511627776 : decimal;
}