js 时间格式化

/**
* 获取本周、本季度、本月、上月的开始日期、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  
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);  
}