Number format in javascript

export function number_format(number, decimals, dec_point, thousands_sep) {
  if (number == null || !isFinite(number)) {
    return number;
  }
  if (!decimals) {
    let lengthOfNumber = number.toString().split('.').length;
    decimals = lengthOfNumber > 1 ? lengthOfNumber : 0;
  }
  if (!dec_point) {
    dec_point = '.';
  }
  if (!thousands_sep) {
    thousands_sep = ',';
  }
  number = parseFloat(number).toFixed(decimals);
  number.replace('.', dec_point);
  let splitNumber = number.split(dec_point);
  splitNumber[0] = splitNumber[0].replace(/\B(?=(\d{3})+(?!\d))/g, thousands_sep);
  number = splitNumber.join(dec_point);

  return number
}