js得到当前月第一天为星期几，当前月共有多少天

var date = new Date(); date.setDate(1); var week = date.getDay(); var weeks; var constDayOfWeek = []; for(var j=week;j<=7+week;j++){if((j%7)==1){weeks="一";}else if((j%7)==2){weeks="二";}else if((j%7)==3){weeks="三";}else if((j%7)==4){weeks="四";}else if((j%7)==5){weeks="五";}else if((j%7)==6){weeks="六";}else if((j%7)==0){weeks="日";}constDayOfWeek.push(weeks); }  date.setMonth(date.getMonth() + 1); var lastDate = new Date(date - 3600000*24); //alert("本月最后一天是 " + lastDate.getDate());