<ul class="list" id="list">  <li class="in">1</li>  <li class="in">2</li>  <li class="in">3</li>  <li class="in">4</li>  <li class="in">5</li>  <li class="in">6</li>    </ul>

.in{  height: 20px;  line-height: 20px;  width: 20px;  background-color: blue;  text-align: center;  color: white;}

<script>var oList = document.getElementById('list');//新增一個li元素var oAdd = document.createElement('li');//設置新增元素的css樣式oAdd.className = "in";oAdd.style.cssText = 'background-color:red;border-radius:50%';//1s后oAdd替換第0個lisetTimeout(function(){  oList.replaceChild(oAdd,document.getElementsByTagName('li')[0]);  //1s后執行incrementNumber函數  setTimeout(incrementNumber,1000);  },1000);function incrementNumber(){  //獲取oList中第1個li  var oLi1 = document.getElementsByTagName('li')[1];  //若存在則進行替換處理  if(oLi1){     oList.replaceChild(oAdd,oLi1);     setTimeout(incrementNumber,1000);      }}</script>