js实现日期级联效果_javascript技巧

            //先给年下拉框赋内容
            var y = new Date().getFullYear();
            var str = strYYYY.substring(0, strYYYY.length - 9);
            for (var i = (y - 30); i             {
                str += " " + i + " 年" + "\r\n";
            }
            document.form1.YYYY.outerHTML = str + "";

            //赋月份的下拉框
            var str = strMM.substring(0, strMM.length - 9);
            for (var i = 1; i                 str += " " + i + " 月" + "\r\n";
            }
            document.form1.MM.outerHTML = str + "";

            document.form1.YYYY.value = y;
            document.form1.MM.value = new Date().getMonth() + 1;
            var n = MonHead[new Date().getMonth()];
            if (new Date().getMonth() == 1 && IsPinYear(YYYYvalue)) n++;
            writeDay(n); //赋日期下拉框
            document.form1.DD.value = new Date().getDate();
        }

        function YYYYMM(str) //年发生变化时日期发生变化(主要是判断闰平年)
        {
            var MMvalue = document.form1.MM.options[document.form1.MM.selectedIndex].value;
            if (MMvalue == "") { DD.outerHTML = strDD; return; }
            var n = MonHead[MMvalue - 1];
            if (MMvalue == 2 && IsPinYear(str)) n++;
            writeDay(n)
        }

        function MMDD(str) //月发生变化时日期联动
        {
            var YYYYvalue = document.form1.YYYY.options[document.form1.YYYY.selectedIndex].value;
            if (str == "") { DD.outerHTML = strDD; return; }
            var n = MonHead[str - 1];
            if (str == 2 && IsPinYear(YYYYvalue)) n++;
            writeDay(n)
        }

        function writeDay(n) //据条件写日期的下拉框
        {
            var s = strDD.substring(0, strDD.length - 9);
            for (var i = 1; i                 s += " " + i + " 日" + "\r\n";
            document.form1.DD.outerHTML = s + "";
        }

        function IsPinYear(year)//判断是否闰平年
        {
            return (0 == year % 4 && (year % 100 != 0 || year % 400 == 0))
        }