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                        /前端开发
                        
                            /JavaScript
                        
                        /焦点图轮播特效

为什么我这代码轮播图死活都切换不了啊，js的代码就没一次打成功过

我不知道我为什么打js的代码总是没效果出来，明明浏览器js代码没有报错，有也修复了，妈的就是死活不出效果。明明照着教程打永远是这样......

<!DOCTYPE html>
<html>
<head>
<title>轮播图</title>
<meta charset="utf-8">
<style type="text/css">
   *{ margin: 0; padding: 0; text-decoration: none;}
   body { padding: 20px;}
   #container { width: 600px; height: 400px; border: 3px solid #333; overflow: hidden; position: relative;}
   #list { width: 4200px; height: 400px; position: absolute; z-index: 1;}
   #list img { float: left;}
   #buttons { position: absolute; height: 10px; width: 100px; z-index: 2; bottom: 20px; left: 250px;}
   #buttons span { cursor: pointer; float: left; border: 1px solid #fff; width: 10px; height: 10px; border-radius: 50%; background: #333; margin-right: 5px;}
   #buttons .on { background: orangered;}
   .arrow { cursor: pointer; display: none; line-height: 39px; text-align: center; font-size: 36px; font-weight: bold; width: 40px; height: 40px; position: absolute; z-index: 2; top: 180px; background-color: RGBA(0,0,0,.3); color: #fff;}
   .arrow:hover { background-color: RGBA(0,0,0,.7);}
   #container:hover .arrow { display: block;}
   #prev { left: 20px;}
   #next { right: 20px;}

</style>
<script type="text/javascript">
  widows.onload = function () {
          var container = document.getElementById('container');
            var list = document.getElementById('list');
            var buttons = document.getElementById('buttons').getElementsByTagName('span');
            var prev = document.getElementById('prev');
            var next = document.getElementById('next');

            function animate (offset) {
            list.style.left = parseInt(list.style.left) - offset + 'px';
            }

   next.onclick = function () {
    animate(-600);
            }

            prev.onclick = function () {
                animate(600);

}

</script>

</head>
<body >
<div id="container">
    <div id="list" style="left: -600px;">
        <img src="img/5.jpg" alt="5"/>
        <img src="img/1.jpg" alt="1"/>
        <img src="img/2.jpg" alt="2"/>
        <img src="img/3.jpg" alt="3"/>
        <img src="img/4.jpg" alt="4"/>
        <img src="img/5.jpg" alt="5"/>
        <img src="img/1.jpg" alt="1"/>
    </div>
    <div id="buttons">
        <span index="1" class="on"></span>
        <span index="2"></span>
        <span index="3"></span>
        <span index="4"></span>
        <span index="5"></span>
    </div>
    <a href="javascripts:;" class="arrow" id="prev"><</a>
    <a href="javascripts:;" class="arrow" id="next">></a>
</div>