Thousand Separator

export function thousandSeparator(n: number): string {
  const str = n.toString();
  const lastIndex = str.length - 1;
 
  let answer = '';
  for (let i = lastIndex; 0 <= i; i--) {
    if (i !== lastIndex && (lastIndex - i) % 3 === 0) {
      answer = `${str[i]}.${answer}`;
    } else {
      answer = `${str[i]}${answer}`;
    }
  }
  return answer;
  /**
   * One Line Example
   * return n.toLocaleString().replace(/,/g, '.')
   */
}