js获取当月的最后一天

function getCurrentMonthLastDay(){
var current=new Date();
var currentMonth=current.getMonth();
var nextMonth=++currentMonth;

var nextMonthDayOne =new Date(current.getFullYear(),nextMonth,1);

var minusDate=1000*60*60*24;

return new Date(nextMonthDayOne.getTime()-minusDate);
}

function getCurrentMonthFirstDay(){
var current=new Date();
current.setDate(1);
return current;
}