function getOrdinalPosition(n: number):string{
 //check when less than 0 throw err
  if(n < 0)
    throw new Error("Should be a positive number");
  
  //define suffix contain ordinary
  const suffixes = ["th", "st", "nd", "rd"]
  
  //get remain number by module 100
  const lastTwoDigits = n % 100;
  
  //if n between 11 and 13, ordinal number would be `th`
  if(n >= 11 && n <= 13)
    return n + 'th';
  
  //Otherwise, we take the last digit and use it to index into the suffixes array
  const lastDigit = n % 10;
  const suffix = suffixes[lastDigit] || "th"
  
  return n + suffix;
}

console.log(getOrdinalPosition(21));
console.log(getOrdinalPosition(76));
console.log(getOrdinalPosition(33));
console.log(getOrdinalPosition(987654321))
console.log(getOrdinalPosition(12345))
console.log(getOrdinalPosition(9999))