//父亲元素.replaceChild(新，旧)

 1     <ul id="city">
 2         <li id="bj">北京</li>
 3         <li id="sh">上海</li>
 4         <li id="gz">广州</li>
 5     </ul>
 6 
 7     <ul id="color">
 8         <li id="red">红色</li>
 9         <li id="green">绿色</li>
10         <li id="blue">蓝色</li>
11     </ul>
12     <script type="text/javascript">
13         var gzLiElement=document.getElementById("gz");
14         gzLiElement.onclick=function(){
15             var colorElement=document.getElementById("color");
16             //父亲元素.replaceChild(新，旧)
17             document.getElementById("city").replaceChild(colorElement,this);
18             alert("xx");
19         }