利用replaceChild打造简单的吞噬效果【jsDEMO】

<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');
//新增一个li元素
var oAdd = document.createElement('li');
//设置新增元素的css样式
oAdd.className = "in";
oAdd.style.cssText = 'background-color:red;border-radius:50%';
//1s后oAdd替换第0个li
setTimeout(function(){
    oList.replaceChild(oAdd,document.getElementsByTagName('li')[0]);
    //1s后执行incrementNumber函数
    setTimeout(incrementNumber,1000);    
},1000);
function incrementNumber(){
    //获取oList中第1个li
    var oLi1 = document.getElementsByTagName('li')[1];
    //若存在则进行替换处理
    if(oLi1){
         oList.replaceChild(oAdd,oLi1);
         setTimeout(incrementNumber,1000);        
    }
}
</script>