JS获取本周、本季度、本月、上月的开端日期、停止日期

Js代码   
/** 
* 获取本周、本季度、本月、上月的开端日期、停止日期 
*/ 
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 
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();

//格局化日期：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; 
}

//获得本季度的开端月份 
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; 
}

//获得本周的开端日期 
function getWeekStartDate() { 
var weekStartDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek); 
return formatDate(weekStartDate); 
}

//获得本周的停止日期 
function getWeekEndDate() { 
var weekEndDate = new Date(nowYear, nowMonth, nowDay + (6 - nowDayOfWeek)); 
return formatDate(weekEndDate); 
}

//获得本月的开端日期 
function getMonthStartDate(){ 
var monthStartDate = new Date(nowYear, nowMonth, 1); 
return formatDate(monthStartDate); 
}

//获得本月的停止日期 
function getMonthEndDate(){ 
var monthEndDate = new Date(nowYear, nowMonth, getMonthDays(nowMonth)); 
return formatDate(monthEndDate); 
}

//获得上月开端时候 
function getLastMonthStartDate(){ 
var lastMonthStartDate = new Date(nowYear, lastMonth, 1); 
return formatDate(lastMonthStartDate); 
}

//获得上月停止时候 
function getLastMonthEndDate(){ 
var lastMonthEndDate = new Date(nowYear, lastMonth, getMonthDays(lastMonth)); 
return formatDate(lastMonthEndDate); 
}

//获得本季度的开端日期 
function getQuarterStartDate(){

var quarterStartDate = new Date(nowYear, getQuarterStartMonth(), 1); 
return formatDate(quarterStartDate); 
}

//或的本季度的停止日期 
function getQuarterEndDate(){ 
var quarterEndMonth = getQuarterStartMonth() + 2; 
var quarterStartDate = new Date(nowYear, quarterEndMonth, getMonthDays(quarterEndMonth)); 
return formatDate(quarterStartDate); 
}