这串代码怎么什么都显示不出来？
<!DOCTYPE HTML>
<html >
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>系好安全带,准备启航</title>
<script type="text/javascript">
var myDate=new Date();
var week=["星期日","星期一","星期二","星期三","星期四","星期五","星期六"];
var num=myDate.getDay();
document.write(
myDate.getFullYear()+"年"+
myDate.getMonth()+1+"月"+
myDate.getDate()+"日"+
"星期"+ week[num]
)；
var scoreStr = "小明:87;小花:81;小红:97;小天:76;小张:74;小小:94;小西:90;小伍:76;小迪:64;小曼:76";
var group=scoreStr.split(";");
var j=0;
for(var i=0,i<group.length,i++)
{
j += parseInt(group[i].slice(3,5));
}
document.write(Math.round(j/group.length));
</script>
</head>
<body>
</body>
</html>
