js更改HTML样式

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>window.open</title>
<script type="text/javascript">
function a(){var b=confirm("你是否要进入斗鱼")
if(b==true){
    var c=prompt("请输入斗鱼地址")
    if(c!=null){
    a=window.open(c,'_blank','width=3000,height=2000,menubar=yes,toolbar=yes, status=yes,scrollbars=yes');
    }
             }

              }

   function wopen(){dd=window.open("https://hao.360.cn/?safe")}
   function Wclose(){

     a.close()
   }
</script>
</head>
<body>
    <input name="button" type="button" onClick="a()" value="点击输入你想浏览的网页" / >
    <input name="button" type="button" onClick="Wclose()" value="点击关闭网页" / >
    <p id="js">
      heollo
</p>
<script type="text/javascript">
var cs=document.getElementById("js");
cs.style.color="red";
   cs.style.background="#00ffff"
</script>

</body>
</html>

红尘往事，一切随风！