如何使用javascript从下拉列表中删除任何多个选定项

var select = document.getElementById("mySelect");

for (var i = select.options.length - 1; i >= 0; i--) {
  if (select.options[i].selected) {
    select.remove(i);
  }
}

select.selectedIndex = -1;

var select = document.getElementById("mySelect");

for (var i = select.options.length - 1; i >= 0; i--) {
  if (select.options[i].selected) {
    select.remove(i);
  }
}

select.selectedIndex = -1;