JSは今週、本四半期、今月、先月の開始日、停止日を獲得して、ある年のある月は何日間ありますか?

/**
*     、   、  、       、    
*/
var now = new Date(); //    
var nowDayOfWeek = now.getDay(); //        
var nowDay = now.getDate(); //   
var nowMonth = now.getMonth(); //   
var nowYear = now.getYear(); //   
nowYear += (nowYear < 2000) ? 1900 : 0; //

var lastMonthDate = new Date(); //    
lastMonthDate.setDate(1);
lastMonthDate.setMonth(lastMonthDate.getMonth()-1);
var lastYear = lastMonthDate.getYear();
var lastMonth = lastMonthDate.getMonth();

//     ：yyyy-MM-dd
function formatDate(date) {
var myyear = date.getFullYear();
var mymonth = date.getMonth()+1;
var myweekday = date.getDate();

if(mymonth < 10){
mymonth = "0" + mymonth;
}
if(myweekday < 10){
myweekday = "0" + myweekday;
}
return (myyear+"-"+mymonth + "-" + myweekday);
}

//       
function getMonthDays(myMonth){
var monthStartDate = new Date(nowYear, myMonth, 1);
var monthEndDate = new Date(nowYear, myMonth + 1, 1);
var days = (monthEndDate - monthStartDate)/(1000 * 60 * 60 * 24);
return days;
}

//          
function getQuarterStartMonth(){
var quarterStartMonth = 0;
if(nowMonth<3){
quarterStartMonth = 0;
}
if(28){
quarterStartMonth = 9;
}
return quarterStartMonth;
}

//         
function getWeekStartDate() {
var weekStartDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek);
return formatDate(weekStartDate);
}

//         
function getWeekEndDate() {
var weekEndDate = new Date(nowYear, nowMonth, nowDay + (6 - nowDayOfWeek));
return formatDate(weekEndDate);
}

//         
function getMonthStartDate(){
var monthStartDate = new Date(nowYear, nowMonth, 1);
return formatDate(monthStartDate);
}

//         
function getMonthEndDate(){
var monthEndDate = new Date(nowYear, nowMonth, getMonthDays(nowMonth));
return formatDate(monthEndDate);
}

//        
function getLastMonthStartDate(){
var lastMonthStartDate = new Date(nowYear, lastMonth, 1);
return formatDate(lastMonthStartDate);
}

//        
function getLastMonthEndDate(){
var lastMonthEndDate = new Date(nowYear, lastMonth, getMonthDays(lastMonth));
return formatDate(lastMonthEndDate);
}

//          
function getQuarterStartDate(){

var quarterStartDate = new Date(nowYear, getQuarterStartMonth(), 1);
return formatDate(quarterStartDate);
}

//          
function getQuarterEndDate(){
var quarterEndMonth = getQuarterStartMonth() + 2;
var quarterStartDate = new Date(nowYear, quarterEndMonth, getMonthDays(quarterEndMonth));
return formatDate(quarterStartDate);
} 

選択された年の選択を得るには、月が何日ありますか?
var temp=new Date(「選択年/選択月+1/0」);
alert(temp.get Date();
いいです
次はJSで作成した、ある年のある月の何日間のget Days InMonth(year,month)を取得する方法です.

function getDaysInMonth(year,month){
      month = parseInt(month,10)+1;
      var temp = new Date(year+"/"+month+"/0");
      return temp.getDate();
}