javascript - 根据所选选项显示文本

Question

我有一个选项供用户选择"is"或“否”。如果选项选择值“y”文本框“adv1”显示 750。否则为 0.00

   <table>

         <tr>
           <td>Advance Required</td>
           <td><select name="advReq" id="ad">
               <option value="y">Yes</option>
               <option value="n">No</option>
               </select>
           </td>
           <td><input name="adv1" type="text" readonly="readonly" value="" /></td>
       </tr>

   </table>

Answer 1

<script>
     function updateText(val) {
      var $el = document.getElementById("adv1");
      if(val == 'y'){
       $el.value = "$ 750";
      } else {
       $el.value = "0";
      }
     }
    </script>

<select name="advReq" id="ad" onchange="updateText(this.value)">
      <option value="y">Yes</option>
      <option value="n">No</option>
</select>
<input name="adv1" type="text" id="adv1"  value="" />