js insertBefore

     <select id="city" size="4" style="width:50px">

         <option id="hn">湖南</option>

         <option id="hb">湖北</option>

     </select>

       <script type="text/javascript">

           /*创建"新元素"，插入到"湖南"元素之前

           var newOptionElement = document.createElement("option");

           newOptionElement.setAttribute("id","new");

           newOptionElement.innerHTML = "新元素";

           var cityElement = document.getElementById("city");

           var hnElement = document.getElementById("hn");

           cityElement.insertBefore(newOptionElement,hnElement);　　//新元素

         */

           //创建"新元素"，插入到"湖南"元素之后

           var newOptionElement = document.createElement("option");

           newOptionElement.setAttribute("id","new");

           newOptionElement.innerHTML = "新元素";

           var cityElement = document.getElementById("city");

           var hnElement = document.getElementById("hn");        

             //兄弟节点  nextSibling

             cityElement.insertBefore(newOptionElement,hnElement.nextSibling);

      </script>
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