SOURCE

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; //
var lastMonthDate = new Date(); //上月日期
lastMonthDate.setDate(1);
lastMonthDate.setMonth(lastMonthDate.getMonth() - 1);
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
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);
}
//获得上周的开始日期
function getLastWeekStartDate() {
  var weekStartDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek - 7);
  return formatDate(weekStartDate);
}
//获得上周的结束日期
function getLastWeekEndDate() {
  var weekEndDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek - 1);
  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);
}
//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);
}

var ss = getQuarterEndDate();
alert(ss);
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