retorna o valor no formato Currency

function formatCurrency(num) {
num = num.toString().replace(/\$|\,/g,'');
if(isNaN(num)){
num = "0";
}
sign = (num == (num = Math.abs(num)));
num = Math.floor(num*100+0.50000000001);
cents = num%100;
num = Math.floor(num/100).toString();
if(cents<10){
cents = "0" + cents;
}
for (var i = 0; i < Math.floor((num.length-(1+i))/3); i++){
num = num.substring(0,num.length-(4*i+3))+'.'+
num.substring(num.length-(4*i+3));
}
return (((sign)?'':'-') + num + ',' + cents);
}