Nodejs Utililty Methods String to Currency Convert

String.prototype.toCurrency = function() {
  var pattern = /^\d{4,}/;
  return pattern.test(this) ? parseFloat(this).toLocaleString() : this;
};

String.prototype.toCurrency = function(){
  var splitNum = this.split(".");
  var numCurrency = splitNum[0].replace(/\B(?=(\d{3})+(?!\d))/g, ",") + ("." + splitNum[1]);
  return numCurrency;
};

String.prototype.toCurrency = function() {
  var isNumberRegex = /^[0-9]+(\.[0-9]+)?$/;
  if (!isNumberRegex.test(this)) {
    return NaN;
  return parseFloat(Number(this).toFixed(2))
    .toString()
    .replace(/(\d)(?=(\d{3})+(?!\d))/g, '$1,');
};
...

String.prototype.toCurrency = function() {
  var pattern = /(\d)(?=(\d{3})+(?=\.))/g
  return this.toString().replace(pattern, "$1,");
};

String.prototype.toCurrency = function(rounder) {
    aDigits = parseFloat(this).toFixed(rounder).split(".");
    aDigits[0] = aDigits[0].split("").reverse().join("")
                                    .replace(/(\d{3})(?=\d)/g, "$1,").split("").reverse().join("");
    return aDigits.join(".");

String.prototype.toCurrency = function(rounder) {
    aDigits = parseFloat(this).toFixed(rounder).split(".");
    aDigits[0] = aDigits[0].split("").reverse().join("")
                                    .replace(/(\d{3})(?=\d)/g, "$1,").split("").reverse().join("");
    return "Rp "+ aDigits.join(".");