colocar comas a cantidades que pasen del mil

number_format.js

function number_format (num) {
            if (!num || num == 'NaN') return '-';
            if (num == 'Infinity') return '∞';
            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);
        }