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);    
	
	//格式化日期：yyyy-MM-dd HH:MM:SS
    var myHour = date.getHours();    
    var myMinute = date.getMinutes();    
    var mySecond = date.getSeconds();    
    if(myHour < 10){   
        myHour = "0" + myHour;   
    }    
    if(myMinute < 10){   
        myMinute = "0" + myMinute;   
    }       
    if(mySecond < 10){   
        mySecond = "0" + mySecond;   
    }       
    return (myyear+"-"+mymonth + "-" + myweekday+" "+myHour+":"+myMinute+":"+mySecond);    
}    
  
//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;   
}   

 //获得本天(i=0)的开始时间   
function getDayStartDate(i) {    
    var nowStartDay = new Date(nowYear, nowMonth, nowDay+i);    
    return formatDate(nowStartDay);   
}  
  
//获得本天(i=0)的结束时间   
function getDayEndDate(i) {    
    var nowStartDay = new Date(nowYear, nowMonth, nowDay+i,23,59,59);    
    return formatDate(nowStartDay);   
}

 //获得本周(i=0)的开始日期   
function getWeekStartDate(i) {    
    //var weekStartDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek);    
    var weekStartDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek+7*i);    
    return formatDate(weekStartDate);   
}    
  
//获得本周的结束日期   
function getWeekEndDate(i) {    
   // var weekEndDate = new Date(nowYear, nowMonth, nowDay + (6 - nowDayOfWeek));    
    var weekEndDate = new Date(nowYear, nowMonth, nowDay + (6 - nowDayOfWeek)+7*i,23,59,59);    
    return formatDate(weekEndDate);   
}    
  
//获得本月的开始日期   
function getMonthStartDate(i){   
    //var monthStartDate = new Date(nowYear, nowMonth, 1);    
    var monthStartDate = new Date(nowYear, nowMonth+i, 1);    
    return formatDate(monthStartDate);   
}   
  
//获得本月的结束日期   
function getMonthEndDate(i){   
    //var monthEndDate = new Date(nowYear, nowMonth, getMonthDays(nowMonth));    
    var monthEndDate = new Date(nowYear, nowMonth+i, getMonthDays(nowMonth+i,),23,59,59);    
    return formatDate(monthEndDate);   
}   
  
//获得本季度的开始日期   
function getQuarterStartDate(i){   
    //var quarterStartDate = new Date(nowYear, getQuarterStartMonth(), 1);    
    var quarterStartDate = new Date(nowYear, getQuarterStartMonth()+3*i, 1);    
    return formatDate(quarterStartDate);   
}   
  
//或的本季度的结束日期   
function getQuarterEndDate(i){   
    var quarterEndMonth = getQuarterStartMonth()+3*i + 2;   
    //var quarterStartDate = new Date(nowYear, quarterEndMonth, getMonthDays(quarterEndMonth));    
    var quarterStartDate = new Date(nowYear, quarterEndMonth, getMonthDays(quarterEndMonth),23,59,59);    
    return formatDate(quarterStartDate);   
}   
  
//获得本年度的开始日期   
function getYearStartDate(i){   
    var quarterStartDate = new Date(nowYear+i, 0, 1);    
    return formatDate(quarterStartDate);   
}  

//获得本年度的结束日期   
function getYearEndDate(i){   
    var quarterStartDate = new Date(nowYear+i, 11, getMonthDays(11),23,59,59);    
    return formatDate(quarterStartDate);   
}  

alert(getMonthStartDate(1));   
</script>