js中计算一个时间点加上一个时间段后的时间

function aa(a,b){
  console.log(111,a,b)
  var nd = new Date(Date.parse(a.replace(/-/g, "/"))); //改为标准格式：2016/04/05 09:29:15
  nd = nd.valueOf(); //转换为毫秒数
  nd = nd + Number(b)
  nd = new Date(nd);
  var y = nd.getFullYear();
  var m = nd.getMonth()+1;
  var d = nd.getDate();
  var hh = nd.getHours();
  var mm = nd.getMinutes();
  var ss = nd.getSeconds();
  if(m <= 9) m = "0"+m;
  if(d <= 9) d = "0"+d; 
  if(hh<= 9) hh = "0"+hh;
  if(mm<= 9) mm = "0"+mm;
  if(ss<= 9) ss = "0"+ss;
  var date = y+"-"+m+"-"+d+" "+hh+":"+mm+":"+ss;
  return date; //结束时间 2016-04-07 13:34:15
};
console.log(aa('2020-11-23 00:00:00', 60*1000))