getYearWeek

function getYearWeek(ymd){
  let _ds = new Date(ymd);      
  _sDate = new Date(_ds.getFullYear(), 0, 1)
  _days = Math.round((ds.valueOf() - _sDate.valueOf()) / 86400000)  //24 *60*60 *1000 
  return Math.ceil(_days/7)
}