Select2不选择在SELECT下拉列表中选择的默认选项

Question

我有一个具有多个属性的下拉选择元素，并且已经选择了多个选项，因此，当我在此下拉列表上初始化select2时，即未选择下拉列表中的所有选定选项。仅当一个选项已选择属性时，它才起作用；如果它具有多个属性，则它无法选择所有属性。

<select name="mydropdown" multiple="multiple">
   <option value="1">All Media</option>
   <option value="3" selected="selected">Social (Organic)</option>
   <option value="4" selected="selected">CRM</option>
   <option value="5" selected="selected">Marketing Ad</option>
   <option value="6">OOH</option>
   <option value="7">Print</option>
   <option value="8">Offsite</option>
   <option value="9">Corporate (Logo)</option>
</select>

Answer 1

[Select2 Basic Usage-https://select2.org/getting-started/basic-usage

[Programmatic Controls-https://select2.org/programmatic-control/add-select-clear-items

$(document).ready(function() {
  $('.js-example-basic-multiple').select2();
});

$('.js-example-basic-multiple').val(['3', '4', '5']);
$('.js-example-basic-multiple').trigger('change');

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.10/js/select2.min.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.10/css/select2.min.css" rel="stylesheet"/>

<select class="js-example-basic-multiple" name="states[]" multiple="multiple">
  <option value="1">All Media</option>
  <option value="3">Social (Organic)</option>
  <option value="4">CRM</option>
  <option value="5">Marketing Ad</option>
  <option value="6">OOH</option>
  <option value="7">Print</option>
  <option value="8">Offsite</option>
  <option value="9">Corporate (Logo)</option>
</select>