基于insertBefore制作简单的循环插空效果_javascript技巧

  

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

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%';
//添加到oList中
oList.insertBefore(oAdd,null);
var num = -1;
var max = oList.children.length;
function incrementNumber(){
 num++;
 //oList.getElementsByTagName('li')[max]相当于null，所以不报错
 oList.insertBefore(oAdd,oList.getElementsByTagName('li')[num]); 
 if(num == max){
  num = -1;
 } 
 if(num == 0){
  num = 1;
 }
 setTimeout(incrementNumber,1000);
}
setTimeout(incrementNumber,1000);