// Extend the default Number object with a formatMoney() method:
// usage: someVar.formatMoney(decimalPlaces, symbol, thousandsSeparator, decimalSeparator)
// defaults: (2, "$", ",", ".")
Number.prototype.formatMoney = function (places, symbol, thousand, decimal) {
  places = !isNaN(places = Math.abs(places)) "$";
  thousand = thousand || ",";
  decimal = decimal || ".";
  var number = this,
    negative = number < 0 "-" : "",
    i = parseInt(number = Math.abs(+number || 0).toFixed(places), 10) + "",
    j = (j = i.length) > 3 "") + i.substr(j).replace(/(\d{3})("$1" + thousand) + (places "");
};

// Default usage and custom precision/symbol :
var revenue = 12345678;
alert(revenue.formatMoney()); // $12,345,678.00
alert(revenue.formatMoney(0, "HK$ ")); // HK$ 12,345,678

// European formatting:
var price = 4999.99;
alert(price.formatMoney(2, "?", ".", ",")); // ?4.999,99

// It works for negative values, too:
alert((-500000).formatMoney(0, "£ ")); // £ -500,000

var price = (12345.99).formatMoney(); // "$12,345.99"

// Remove non-numeric chars (except decimal point/minus sign):
priceVal = parseFloat(price.replace(/[^0-9-.]/g, '')); // 12345.99

// To set it up as a global function:
function formatMoney(number, places, symbol, thousand, decimal) {
  number = number || 0;
  places = !isNaN(places = Math.abs(places)) "$";
  thousand = thousand || ",";
  decimal = decimal || ".";
  var negative = number < 0 "-" : "",
    i = parseInt(number = Math.abs(+number || 0).toFixed(places), 10) + "",
    j = (j = i.length) > 3 "") + i.substr(j).replace(/(\d{3})("$1" + thousand) + (places "");
}

// To create it as a library method:
myLibrary.formatMoney = function (number, places, symbol, thousand, decimal) {
  /* as above */
}

// Example usage:
formatMoney(54321); // $54,321
myLibrary.formatMoney(12345, 0, "£ "); // £ 12,345