年月日的计算

// type:年、月或者日
// data:日期
// 加减量
function addOrReduceDate(type,date,num) {
  var nowDate = null;
  var strDate = "";
  num = parseInt(num); // 防止传入字符串报错
  var seperator1 = "-";
  var seperator2 = ":";
  if(date == "") {
    nowDate = new Date();
  } else {
    nowDate = new Date(date);
  }
 
  if(type==="Y"){
    nowDate.setFullYear(nowDate.getFullYear() + num);
  }
  if(type==="M"){
    nowDate.setMonth(nowDate.getMonth() + num);
  }
  if(type==="D"){
    nowDate.setDate(nowDate.getDate() + num);
  }
  if(type==="A"){
    nowDate.setFullYear(nowDate.getFullYear() + num);
    nowDate.setMonth(nowDate.getMonth() + num);
    nowDate.setDate(nowDate.getDate() + num);
  }
  var year = nowDate.getFullYear(); // 年
  var month = nowDate.getMonth() + 1; // 月
  strDate = nowDate.getDate(); //日
  var hours = nowDate.getHours(); // 时
  var minutes = nowDate.getMinutes(); // 分
  var seconds = nowDate.getSeconds(); // 秒
  if(month >= 1 && month <= 9) {
    month = "0" + month;
  }
  if(strDate >= 0 && strDate <= 9) {
    strDate = "0" + strDate;
  }
  if(seconds >= 0 && seconds <= 9) {
    seconds = "0" + seconds;
  }
  // var dateStr = year + seperator1 + month + seperator1 + strDate + " " + hours + seperator2 + minutes + seperator2 + seconds;
  var dateStr = year + seperator1 + month + seperator1 + strDate;

  console.log(dateStr)
  return dateStr;
}

let resy=  addOrReduceDate("M",formState.riqi,formState.youxiaoqi);