js得到某月有多少天

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XX   http://www.cnblogs.com/goodspeed    XX
XX   /archive/2004/08/12/32551.html      XX
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//方法一
function DayNumOfMonth(Year,Month)
{
    var d = new Date(Year,Month,0);
    return d.getDate();
}
//方法二
function DayNumOfMonth(Year,Month)
{
    Month--;
    var d = new Date(Year,Month,1);
    d.setDate(d.getDate()+32-d.getDate());
    return (32-d.getDate());
}
//方法三
function DayNumOfMonth(Year,Month)
{
    return 32-new Data(year,month,32).getData();
}