js日期、星座的级联显示代码

js 代码
代码如下:
    function birthdayOnchange(obj) {
        var year = $("<%= DDL_Year.ClientID%>").value;

        if (year == "year")
            return;
        else
            year = parseInt(year, 10);

        var month = $("<%=DDL_Month.ClientID%>").value;
        if (month == "month")
            return;
        else
            month = parseInt(month, 10);

        var day = $("<%=DDL_Day.ClientID%>").value;
        var wholeday = getDays(year, month);

        if (1) {
            var options = $("<%=DDL_Day.ClientID%>").options;
            for (var i = 1; i <= wholeday; i++) {
                var j = i.toString();
                j = j.length == 1 ? "0" + j : j;
                options.length = i + 1;
                options[i].value = j;
                options[i].text = j;
                if (day <= wholeday && i == day) {
                    options[i].selected = true;
                }
            }
        }
    }

 function getDays(year, month) {
        var dayarr = new Array(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

        if (month == 2) {
            if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0 || year < 1900)
                return 29;
            else
                return dayarr[month - 1];