js給當前日期加一天

<script type="text/javascript">
    function addDay(datetime, days) {
        var old_time = new Date(datetime.replace(/-/g, "/")); //替換字符，js不認2013-01-31,只認2013/01/31
        var fd = new Date(old_time.valueOf() + days * 24 * 60 * 60 * 1000); //日期加上指定的天數
        var new_time = fd.getFullYear() + "-";
        var month = fd.getMonth() + 1;
        if (month >= 10) {
            new_time += month + "-";
        } else {
            //在小於10的月份上補0
            new_time += "0" + month + "-";
        }
        if (fd.getDate() >= 10) {
            new_time += fd.getDate();
        } else {
            //在小於10的日期上補0
            new_time += "0" + fd.getDate();
        }
        return new_time; //輸出格式：2013-01-02
    }

    alert(addDay("2013-11-12", 1)); //彈出值：2013-11-13
</script>