获取上个月，三个月，上一年的日期

//获得上个月在这一天的日期
function getLastMonthToday(date){
var daysInMonth = new Array([0],[31],[28],[31],[30],[31],[30],[31],[31],[30],[31],[30],[31]);
var strYear = date.getFullYear();
var strDay = date.getDate();
var strMonth = date.getMonth()+1;
if(strYear%4 == 0 && strYear%100 != 0){
daysInMonth[2] = 29;
}
if(strMonth - 1 == 0)
{
strYear -= 1;
strMonth = 12;
}
else
{
strMonth -= 1;
}
strDay = daysInMonth[strMonth] >= strDay ? strDay : daysInMonth[strMonth];
if(strMonth<10)
{
strMonth=“0”+strMonth;
}
if(strDay<10)
{
strDay=“0”+strDay;
}
datastr = strYear+"-"+strMonth+"-"+strDay;
return datastr;
}
function getToday(date) {
var daysInMonth = new Array([0], [31], [28], [31], [30], [31], [30], [31], [31], [30], [31], [30], [31]);
var strYear = date.getFullYear();
var strDay = date.getDate();
var strMonth = date.getMonth() + 1;
strDay = daysInMonth[strMonth] >= strDay ? strDay : daysInMonth[strMonth];
if (strMonth < 10) {
strMonth = “0” + strMonth;
}
if (strDay < 10) {
strDay = “0” + strDay;
}
datastr = strYear + “-” + strMonth + “-” + strDay;
return datastr;
}
//获得前三个月在这一天的日期
function getThreeMonthToday(date){
var daysInMonth = new Array([0],[31],[28],[31],[30],[31],[30],[31],[31],[30],[31],[30],[31]);
var strYear = date.getFullYear();
var strDay = date.getDate();
var strMonth = date.getMonth()+1;
if(strYear%4 == 0 && strYear%100 != 0){
daysInMonth[2] = 29;
}
if(strMonth - 3 == 0)
{
strYear -= 1;
strMonth = 12;
}else if(strMonth - 3 < 0){
strMonth = 12-(3 - strMonth );
}else{
strMonth -= 3;
}
strDay = daysInMonth[strMonth] >= strDay ? strDay : daysInMonth[strMonth];
if(strMonth<10)
{
strMonth=“0”+strMonth;
}
if(strDay<10)
{
strDay=“0”+strDay;
}
datastr = strYear+"-"+strMonth+"-"+strDay;
return datastr;
}
//获得一年前在这一天的日期
function getLastYearToday(date){
var daysInMonth = new Array([0],[31],[28],[31],[30],[31],[30],[31],[31],[30],[31],[30],[31]);
var strYear = date.getFullYear()-1;
var strDay = date.getDate();
var strMonth = date.getMonth()+1;
if(strYear%4 == 0 && strYear%100 != 0){
daysInMonth[2] = 29;
}
strDay = daysInMonth[strMonth] >= strDay ? strDay : daysInMonth[strMonth];
if(strMonth<10)
{
strMonth=“0”+strMonth;
}
if(strDay<10)
{
strDay=“0”+strDay;
}
datastr = strYear+"-"+strMonth+"-"+strDay;
return datastr;
}
// 传天数 获取多少天之前后之后的日期
function addDate(days) {
var d = new Date();
d.setDate(d.getDate() + days);
var month = d.getMonth() + 1;
var day = d.getDate();
if (month < 10) {
month = “0” + month;
}
if (day < 10) {
day = “0” + day;
}
var val = d.getFullYear() + “-” + month + “-” + day;
return val;
}