JavaScript Money Format

money-format.js

 Number.prototype.formatMoney = function(places, symbol, thousand, decimal) {
	places = !isNaN(places = Math.abs(places)) ? places : 2;
	symbol = symbol !== undefined ? symbol : "$";
	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 ? j % 3 : 0;
	return symbol + negative + (j ? i.substr(0, j) + thousand : "") + i.substr(j).replace(/(\d{3})(?=\d)/g, "$1" + thousand) + (places ? decimal + Math.abs(number - i).toFixed(places).slice(2) : "");
};


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

// European formatting:
var price = 4999.99;
console.log(price.formatMoney(2, "€", ".", ",")); // €4.999,99

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