function formatThousand(num) {

    num = num + "";

    var reg = /(-?\d+)(\d{3})/;

    while (reg.test(num)) {

        var temp = num.replace(reg, "$1,$2");

        if (num.indexOf(".") >= 0 && temp.split(".")[1].length > num.split(".")[1].length) {

            break;

        }

        num = temp;

    }

    return num;

}