如何在javascript中设置select2下拉菜单的selectedindex

<select id="mySelect">
  <option value="1">Option 1</option>
  <option value="2">Option 2</option>
  <option value="3">Option 3</option>
</select>

$(document).ready(function() {
  $('#mySelect').select2(); // 初始化select2插件

  // 设置选中项的索引为2
  $('#mySelect').val('2').trigger('change');
});

document.addEventListener('DOMContentLoaded', function() {
  var selectElement = document.getElementById('mySelect');
  var select2Instance = new Select2(selectElement); // 初始化select2插件

  // 设置选中项的索引为2
  select2Instance.val('2').trigger('change');
});