<input type="radio" name="gender" value="male"> Male
<input type="radio" name="gender" value="female"> Female

<script>
  var gender = ""; // 用于存储选择的值

  // 监听单选按钮的改变事件
  var radios = document.getElementsByName("gender");
  for (var i = 0; i < radios.length; i++) {
    radios[i].addEventListener("change", function() {
      gender = this.value; // 将选中的值存储在变量中
    });
  }
</script>

<select id="genderSelect">
  <option value="male">Male</option>
  <option value="female">Female</option>
</select>

<script>
  // 初始化select2插件
  $("#genderSelect").select2();

  // 监听单选按钮的改变事件
  var radios = document.getElementsByName("gender");
  for (var i = 0; i < radios.length; i++) {
    radios[i].addEventListener("change", function() {
      var selectedValue = this.value; // 获取选中的值
      $("#genderSelect").val(selectedValue).trigger("change"); // 将选中的值应用到select2插件
    });
  }
</script>