js获取本月开始时间和结束时间

var firstDate = new Date();
        var startDate = firstDate.getFullYear()+"-"+((firstDate.getMonth()+1)<10?"0":"")+(firstDate.getMonth()+1)+"-"+"01";
        //alert(firstDate.getFullYear()+"-"+((firstDate.getMonth()+1)<10?"0":"")+(firstDate.getMonth()+1)+"-"+"01");

        var date=new Date();
        var currentMonth=date.getMonth();
        var nextMonth=++currentMonth;
        var nextMonthFirstDay=new Date(date.getFullYear(),nextMonth,1);
        var oneDay=1000*60*60*24;
        var lastDate =  new Date(nextMonthFirstDay-oneDay);
        var  endDate = lastDate.getFullYear()+"-"+((lastDate.getMonth()+1)<10?"0":"")+(lastDate.getMonth()+1)+"-"+(lastDate.getDate()<10?"0":"")+lastDate.getDate();
        //alert(lastDate.getFullYear()+"-"+((lastDate.getMonth()+1)<10?"0":"")+(lastDate.getMonth()+1)+"-"+(lastDate.getDate()<10?"0":"")+lastDate.getDate());

}