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>