JS操作CSS

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript">


   //产生一个四位的验证码。
   function createCode(){
       var datas = ['A','B','何','敏','凡','江','1','9']; // 0-7 长度8
       var code = "";
       for(var i = 0 ; i<4; i++){
           //随机产生四个索引值
           var index = Math.floor(Math.random()*datas.length); // random 0.0-1.0（不包括1.0）
           code+=datas[index];
       }

       var spanNode = document.getElementById("code");
       spanNode.innerHTML = code;
       spanNode.style.fontSize ="24px";
       spanNode.style.color = "red";
       spanNode.style.backgroundColor="gray";
       spanNode.style.textDecoration = "line-through";
   }

function ready(){
   createCode();
}


</script>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>
<body onload="ready()">
   <span id="code"></span><a href="#" onclick="createCode()">看不清，换一个</a>

</body>
</html>