js获得本周，本月，本季度的开始日期和结束日期

<script>  
var now = new Date();                    //当前日期  
var nowDayOfWeek = now.getDay();         //今天本周的第几天  
var nowDay = now.getDate();              //当前日  
var nowMonth = now.getMonth();           //当前月  
var nowYear = now.getYear();             //当前年  
nowYear += (nowYear < 2000) ? 1900 : 0;  //  
 
//格式化日期：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);   
}   
 
//获得某月的天数  
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;   
}  
 
//获得本季度的开始月份  
function getQuarterStartMonth(){  
    var quarterStartMonth = 0;  
    if(nowMonth<3){  
       quarterStartMonth = 0;  
    }  
    if(2<nowMonth && nowMonth<6){  
       quarterStartMonth = 3;  
    }  
    if(5<nowMonth && nowMonth<9){  
       quarterStartMonth = 6;  
    }  
    if(nowMonth>8){  
       quarterStartMonth = 9;  
    }  
    return quarterStartMonth;  
}  
 
//获得本周的开始日期  
function getWeekStartDate() {   
    var weekStartDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek);   
    return formatDate(weekStartDate);  
}   
 
//获得本周的结束日期  
function getWeekEndDate() {   
    var weekEndDate = new Date(nowYear, nowMonth, nowDay + (6 - nowDayOfWeek));   
    return formatDate(weekEndDate);  
}   
 
//获得本月的开始日期  
function getMonthStartDate(){  
    var monthStartDate = new Date(nowYear, nowMonth, 1);   
    return formatDate(monthStartDate);  
}  
 
//获得本月的结束日期  
function getMonthEndDate(){  
    var monthEndDate = new Date(nowYear, nowMonth, getMonthDays(nowMonth));   
    return formatDate(monthEndDate);  
}  
 
//获得本季度的开始日期  
function getQuarterStartDate(){  
      
    var quarterStartDate = new Date(nowYear, getQuarterStartMonth(), 1);   
    return formatDate(quarterStartDate);  
}  
 
//或的本季度的结束日期  
function getQuarterEndDate(){  
    var quarterEndMonth = getQuarterStartMonth() + 2;  
    var quarterStartDate = new Date(nowYear, quarterEndMonth, getMonthDays(quarterEndMonth));   
    return formatDate(quarterStartDate);  
}  
 
alert(getQuarterEndDate());  
</script>