<html>
<head>
<title></title>
<script language ="javascript" type="text/javascript">
//比较date是否相等。如果相等则不再处理;否则转到当前月份上上一个月份的最后一天
function OverRideSetMonth(d,num)
{
var oldDate = d.getDate();
d.setMonth(d.getMonth()+num);
var newDate = d.getDate();
if(oldDate!=newDate){//改动到上一月的月末
d.setDate(1-1);
}
return d;
}
var d = new Date('2012', '4', '31');
alert(OverRideSetMonth(d,1));
</script>
</head>
<body>
</body>
</html>