手风琴效果

<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
ul{list-style: none}
*{margin:0; padding:0;}
div{
1150px;
height: 400px;
margin:50px auto;
border:1px solid red;
overflow: hidden;
}
div li {
240px;
height: 400px;
float: left;
}
div ul {
1300px;
}
</style>
</head>
<body>
    <div>
     <ul>
     <li></li>
     <li></li>
     <li></li>
     <li></li>
     <li></li>
     </ul>
    </div>
</body>
</html>
<script src="sport4.js"></script>
<script type="text/javascript">
//页面打开后 通过遍历li为每一个li添加一个背景图片
var list = document.getElementsByTagName("li");
for( var i = 0 ; i < list.length ; i++ ){
    list[i].style.background = `url(images/${i+1}.jpg)`;
    //鼠标移入到某个li上 当前的li 宽度变大800 其余100
    list[i].onmouseover = function(){
        for( var j = 0 ; j < list.length ; j++ ){
            startMove( list[j],{"width":100} );
        }
        startMove( this,{"width":800} );
    }
    //鼠标离开 恢复li的宽度为 240
    list[i].onmouseout = function(){
        for( var j = 0 ; j < list.length ; j++ ){
            startMove( list[j],{"width":240} );
        }
    }
}
</script>