如何取得下拉列表的顯示值

<select size="1" name="s_dept">  
  <option value="EP4110">臘模</option>  
  <option value="EP4115">浸漿</option>  
  <option value="EP4120">鑄造</option>  
  <option value="EP4130">處理</option>
  <option value="EP41331">大發處理=＞製六</option>
  <option value="EP41332">大發處理=＞焊蓋</option>
  <option value="EP41333">大發處理=＞NPS</option>
  <option value="EP41335">大發處理=＞報廢</option>
  <option value="EP4210">製六部</option>
  <option value="EP4200">焊蓋</option>
  <option value="EP4310">製一部-NPS</option>
  <option value="EP4320">製二部-NPS</option>
  <option value="EP4330">製三部-NPS</option>
  <option value="EP4410">組桿-MW</option>
  <option value="EP4420">組桿-IH</option>
  <option value="EP4430">組桿-PT</option>
  <option value="SEL" selected>請選擇一部門</option>
  </select>
如何取得這個下拉列表的顯示值：
臘模,
浸漿
...........

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<script>
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<select name="s_dept" onChange="a(this.options[this.options.selectedIndex].value)">
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<select name="s_dept" onChange="a(this.options[this.options.selectedIndex].text)">
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