jQuery：将选中的文本作为逗号与选择框分开

<select id="testID" multiple="multiple">
   <option value="1">test Value1</option>
   <option value="2">test Value2</option>
   <option value="3">test Value3</option>
   <option value="4">test Value4</option>
   <option value="5">test Value5</option>
  <option value="6">test Value6</option>
</select>

<input type="button" value="Get dropdown selected Value" id ="select-values">
<select id="testID" multiple="multiple">
   <op