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);
  num = Math.floor(num / 100).toString();
  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);
}