JS实现获取进今年第几天是周几的方法分析

function getWeek(str){
  var nowyearstr =Date.parse(new Date().getFullYear());
  var nowstr =nowyearstr+str86400000;
  return new Date(nowstr).getDay();
}

<script>
function getWeek(str){
  var nowyearstr =Date.parse(new Date().getFullYear());
  var nowstr =nowyearstr+str86400000;
  return new Date(nowstr).getDay();
}
document.write(getWeek(100))
</script>

function getWeek(str){
  var nowyearstr =Date.parse(new Date().getFullYear());
  var nowstr =nowyearstr+(str-1)86400000;
  return new Date(nowstr).getDay();
}

function as(dy){
  return ['日', '一', '二', '三', '四', '五', '六'][new Date(new Date().getFullYear(), 0, dy % 7).getDay()];
}