JS 年月日连动

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<html>
<head>
<title> New Document </title>
<meta name="Generator" content="EditPlus">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<script language="javascript">
function   YYYYMMDDstart()
{
          MonHead   =   [31,   28,   31,   30,   31,   30,   31,   31,   30,   31,   30,   31];

          //先给年下拉框赋内容
          var   y       =   new   Date().getFullYear();
          for   (var   i   =   (y-30);   i   <   (y-10);   i++)   //以今年为准，显示前30年之后的20年
                  document.form1.YYYY.options.add(new   Option(""+i+"",   i));

          //赋月份的下拉框
          for   (var   i   =   1;   i   <   13;   i++)
                  document.form1.MM.options.add(new   Option(""+i+"",   i));

//          document.form1.YYYY.value   =   y;   //获取到当前年份
//          document.form1.MM.value   =   new   Date().getMonth()   +   1;   获取到当前月份
          var   n   =   MonHead[new   Date().getMonth()];
          if   (new   Date().getMonth()   ==1   &&   IsPinYear(YYYYvalue))   n++;
                  writeDay(n);   //赋日期下拉框Author:meizz
//          document.form1.DD.value   =   new   Date().getDate();   获取到当前日期
}
function   YYYYDD(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   ==   ""){   var   e   =   document.form1.DD;   optionsClear(e);   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   (YYYYvalue   ==   ""){   var   e   =   document.form1.DD;   optionsClear(e);   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   e   =   document.form1.DD;   optionsClear(e);
          for   (var   i=1;   i<(n+1);   i++)
                  e.options.add(new   Option(""+i+"",   i));
}
function   IsPinYear(year)//判断是否闰平年
{       return(0   ==   year%4   &&   (year%100   !=0   ||   year%400   ==   0));}
function   optionsClear(e)
{
          for   (var   i=e.options.length;   i>0;   i--)
                  e.remove(i);
}
</script>
</head>