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年月日三級聯動選單

<html>
<head>
<title>年月日三下拉框聯動</title>
<meta http-equiv='Content-Type' content='text/html; charset=gb2312'>
</head>

<body>
<form name=form1>
<select name=YYYY onchange="YYYYMM(this.value)">
<option value="">請選擇 年</option>
</select>
<select name=MM onchange="MMDD(this.value)">
<option value="">選擇 月</option>
</select>
<select name=DD>
<option value="">選擇 日</option>
</select>
</form>

<script language="JavaScript">

<!--
function window.onload()
{
strYYYY = document.form1.YYYY.outerHTML;
strMM = document.form1.MM.outerHTML;
strDD = document.form1.DD.outerHTML;
MonHead = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];

//先給年下拉框賦內容
var y = new Date().getFullYear();
var str = strYYYY.substring(0, strYYYY.length - 9);
for (var i = (y-30); i < (y+30); i++) //以今年為準,前30年,後30年
{
str += "<option value='" + i + "'> " + i + " 年" + "</option>\r\n";
}
document.form1.YYYY.outerHTML = str +"</select>";

//賦月份的下拉框
var str = strMM.substring(0, strMM.length - 9);
for (var i = 1; i < 13; i++)
{
str += "<option value='" + i + "'> " + i + " 月" + "</option>\r\n";
}
document.form1.MM.outerHTML = str +"</select>";

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(y)) n++;
writeDay(n); //賦日期下拉框
document.form1.DD.value = new Date().getDate();
}
function YYYYMM(str) //年發生變化時日期發生變化(主要是判斷閏平年)
{
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) //月發生變化時日期聯動
{
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) //據條件寫日期的下拉框
{
var s = strDD.substring(0, strDD.length - 9);
for (var i=1; i<(n+1); i++)
s += "<option value='" + i + "'> " + i + " 日" + "</option>\r\n";
document.form1.DD.outerHTML = s +"</select>";
}
function IsPinYear(year)//判斷是否閏平年
{ return(0 == year%4 && (year%100 !=0 || year%400 == 0))}
//-->

</script>
</body>
</html>