尝试使用ajax插入多选输入

<select id="multiSelect" multiple>
  <option value="option1">选项1</option>
  <option value="option2">选项2</option>
  <option value="option3">选项3</option>
  <option value="option4">选项4</option>
</select>
<button onclick="insertOptions()">插入选项</button>

function insertOptions() {
  var selectElement = document.getElementById("multiSelect");
  
  // 创建新的选项
  var option1 = document.createElement("option");
  option1.value = "option5";
  option1.text = "选项5";
  
  var option2 = document.createElement("option");
  option2.value = "option6";
  option2.text = "选项6";
  
  // 将新的选项插入到多选输入框中
  selectElement.add(option1);
  selectElement.add(option2);
}