js Date ()

function getPreDay(today){

  let yesterday_milliseconds=today.getTime()-1000*60*60*24;//前一天
  let yesterday=new Date();
  yesterday.setTime(yesterday_milliseconds);
  let strYear=yesterday.getFullYear();
  let strDay=yesterday.getDate();
  let strMonth=yesterday.getMonth()+1;
  if(strMonth<10)
  {
    strMonth="0"+strMonth;
  }
  if(strDay<10)
  {
    strDay="0"+strDay;
  }
  let strYesterday=strYear+"-"+strMonth+"-"+strDay;
  return strYesterday
}