选择 年 月 日后 计算出该月共有几周，动态显示在select中
关键字：my97 、当前月周总数
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript" src="js/script.js"></script>
<script type="text/javascript" src="js/jquery-1.6.4.min.js"></script>
<script type="text/javascript" src="js/calendar/WdatePicker.js"></script>
</head>
<body>
<td>当前日期：</td>
<td><input name="startdate" id="startdate" type="text" onFocus="WdatePicker({isShowWeek:true,onpicked:function() {abc();}})"/></td>
<td>请选择周：</td>
<select id="weeksum"></select>
</body>
</html>
<SCRIPT LANGUAGE="JavaScript">
function abc() {
$("#weeksum").html("");
var selectdate =$("#startdate").val().split("-");
var a=selectdate[0];
var b=selectdate[1];
var c=1;
var date = new Date(a, parseInt(b) - 1, 1), w = date.getDay(), d = date.getDate();
//return Math.ceil( (d + 6 - w) / 7 );
var date = new Date();
date.setFullYear(a);
date.setMonth(b);//当前月-1
date.setDate(1);
var weeknumber = date.getDay();//该月第一天是星期几
//alert(weeknumber);
var monthday=30;
//weeknumber+当前月的天数/7
if(a== 1 || a==3 || a== 5 || a==7 || a==8 ||a==10 ||a== 12){//每月多少天
monthday=31;
}
if(a==4 ||a==6 ||a== 9 ||a== 11){
monthday=30;
}
if((a%4==0 && a%100 != 0) || (a%400==0)){
monthday=29;
}
if(!(a%4==0 && a%100 !=0) || (a%400==0)){
monthday=28;
}
//当前月的周数
var weeksum=Math.floor((weeknumber+monthday)/7);//每月多少周，小数舍去了
if((weeknumber+monthday)/7 > Math.floor((weeknumber+monthday)/7)){//如果有小数 总数+1
weeksum +=1;
}
if(weeksum>0){
for(i=1;i<=weeksum;i++){
$("#weeksum").append("<option value='"+i+"' >" +"第"+i+"周"+"</option>");
}
}
}
</SCRIPT>