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);      

}  

 //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);      

//获得本年度的开始日期     

function getyearstartdate(i){     

    var quarterstartdate = new date(nowyear+i, 0, 1);      

//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);      

alert(getmonthstartdate(1));     

</script>