如何在下拉列表/selectlist列表中添加复选框选中项

<select id="mySelect" multiple>
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
  <option value="option4">Option 4</option>
</select>

var select = document.getElementById("mySelect");
select.addEventListener("change", function() {
  updateSelectedOptions(select);
});

function updateSelectedOptions(select) {
  var selectedOptions = [];
  var options = select.options;
  
  for (var i = 0; i < options.length; i++) {
    if (options[i].selected) {
      selectedOptions.push(options[i].value);
    }
  }
  
  // 根据需要进行进一步处理
  console.log(selectedOptions);
}