<select id="mySelect">
  <option value="">-- None --</option>
  <option value="1">Option 1</option>
  <option value="2">Option 2</option>
</select>

<script>
$(document).ready(function() {
  $('#mySelect').select2({
    placeholder: "Select an option",
    allowClear: true
  });
});
</script>

$('#mySelect').select2({
  placeholder: "Select an option",
  allowClear: true
});

$('#mySelect').select2({
  placeholder: "Select an option",
  allowClear: true
});

// 动态添加None选项
$('#mySelect').prepend('<option value="">-- None --</option>').trigger('change');

$('#mySelect').select2({
  placeholder: "Select options",
  allowClear: true
});

// 监听变化，当选择None时清空其他选项
$('#mySelect').on('select2:select', function(e) {
  if (e.params.data.id === "") {
    $(this).val("").trigger("change");
  }
});

$('#mySelect').select2({
  placeholder: "Select an option",
  allowClear: true,
  language: {
    noResults: function() {
      return "No results found";
    },
    searching: function() {
      return "Searching...";
    }
  }
});

$('#mySelect').select2({
  ajax: {
    url: '/api/data',
    dataType: 'json',
    processResults: function(data) {
      // 在远程数据前添加None选项
      data.unshift({id: '', text: '-- None --'});
      return {
        results: data
      };
    }
  },
  placeholder: "Search for an option",
  allowClear: true
});