JavaScript获取某年某月有多少天以及第一天是星期几

function getdaysweekady(year,month)  
{
    var date = new date(year, month-1, 1);//月份是0-11
    var days = new date(date.gettime() - 864e5).getdate();
    var weekday = date.getday();
    console.log(days);
    console.log(weekday)；
}