JS获取本周、本月、上月、本季度的开始日期、结束日期

var now = new Date(); //当前日期
var nowDayOfWeek = now.getDay(); //今天本周的第几天
var nowDay = now.getDate();      //当前日期号
var nowMonth = now.getMonth();   //当前月
var nowYear = now.getYear();     //当前年
nowYear += (nowYear < 2000) ? 1900 : 0; 


var lastMonthDate = new Date(); //上月日期
lastMonthDate.setDate(1);//设置日期为本月1号
lastMonthDate.setMonth(lastMonthDate.getMonth()-1);//设置日期为上个月
var lastYear = lastMonthDate.getYear();
var lastMonth = lastMonthDate.getMonth();

//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 eg：传1获得的为2月份的天数
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+1);
    return formatDate(weekStartDate);
}

//获得本周的结束日期
function getWeekEndDate() {
    var weekEndDate = new Date(nowYear, nowMonth, nowDay + (7 - 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);
}

//获得上月开始时间
function getLastMonthStartDate(){
    var lastMonthStartDate = new Date(nowYear, lastMonth, 1);
    return formatDate(lastMonthStartDate);
}

//获得上月结束时间
function getLastMonthEndDate(){
    var lastMonthEndDate = new Date(nowYear, lastMonth, getMonthDays(lastMonth));
    return formatDate(lastMonthEndDate);
}

//获得本季度的开始日期
function getQuarterStartDate(){
    var quarterStartDate = new Date(nowYear, getQuarterStartMonth(), 1);
    return formatDate(quarterStartDate);
}

//获得本季度的结束日期
function getQuarterEndDate(){
    var quarterEndMonth = getQuarterStartMonth() + 2;
    var quarterStartDate = new Date(nowYear, quarterEndMonth, getMonthDays(quarterEndMonth));
    return formatDate(quarterStartDate);
}