JS获取上个月

1,yyyy-mm-dd获取上个月

function getUpMonth(t){
     var tarr =t.split('-');
     var year =tarr[0];               //获取当前日期的年
     var month =tarr[1];           //获取当前日期的月
     var day =tarr[2];               //获取当前日期的日
     var days =newDate(year,month,0);   
       var year2= year;
     var month2 =parseInt(month)-1;
    if(month2==0) {
        year2 = parseInt(year2)-1;
        month2 = 12;
     }
     var day2 =day;
     var days2 =new Date(year2,month2,0);
     days2 =days2.getDate();
    if(day2>days2) {
        day2 = days2;
     }
    if(month2<10) {
        month2 = '0'+month2;
       var t2 =year2+'-'+month2+'-'+day2;
     returnt2;
 }

2.yyyymm获取上个月

functiongetUpMonth(t){
     var year=t.substring(0,4);           //获取当前日期的年
     var month =t.substring(4,6);             //获取当前日期的月
  
     var year2 =year;
     var month2 =parseInt(month)-1;
    if(month2==0) {
        year2 = parseInt(year2)-1;
        month2 = 12;
     }
     
    if(month2<10) {
        month2 = '0'+month2;
     }
     var m =year2.toString();
     var n=month2.toString();
     var t2 =m+n;
     returnt2;
 }