js 日期操作

// 日期 加减 2015-01-01 +1 -1 返回 yyyy-mm-dd
function addNDays(newdate,daysToAdd){

 var newtimems = newdate.getTime() + (daysToAdd * 24 * 60 * 60 * 1000);
newdate.setTime(newtimems);
return formatDate(newdate);

}
//获取当月最后一天日期
function getFirstAndLastMonthDay( year, month){

var  firstdate = year + '-' + month + '-01';
var  day = new Date(year,month,0); 
var  lastdate = year + '-' + month + '-' + day.getDate();//获取当月最后一天日期  
return lastdate;

}

//获取当月最后一天日期
function getLastMonthDay( year, month){

var firstdate = year + '-' + month + '-01';
var day = new Date(year,month,0); 
var lastdate  = day.getDate();//获取当月最后一天日期  
return lastdate;

}
// 日期加一个月 2015-01 + 1
function addMonth(newdate, daysToAdd) {

var newtimems = newdate.getTime() + (daysToAdd * 1 * 24 * 60 * 60 * 1000);
newdate.setTime(newtimems);
var c = formatMonth(newdate);
return c;

}
// 日期减一个月 2015-01 - 1
function subMonth(newdate,daysToAdd) {

var y =newdate.getFullYear();
var m =newdate.getMonth()+1;
var lastdate = getFirstAndLastMonthDay(y,m);//2015-01-01
var date=getLastMonthDay(y,m);
var lastd = lastdate.split('-');
var newtimems=new Date(lastd[0],parseInt(lastd[1])-1,lastd[2]).getTime()+(daysToAdd*date*24*60*60*1000);
newdate.setTime(newtimems);
var c =formatMonth(newdate);
 return c;

}
// 日期格式话 yyyy-mm
function formatMonth (date) {
var m =date.getMonth()+1;
if(m<10){

   m="0"+m;

}

return date.getFullYear()+"-"+m;

}

// 日期格式话 yyyy-mm-dd
function formatDate(date) {
var m =date.getMonth()+1;
var d = date.getDate();
if(m<10){

   m="0"+m;

}

if(d<10){
   d="0"+d;

}

return date.getFullYear()+"-"+m+"-"+d;

}