求大神解答，为甚么for后面的输不出来
<!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">
//通过javascript的日期对象来得到当前的日期，并输出。
var week=["星期日","星期一","星期二","星期三","星期四","星期五","星期六"];
var currday=new Date();
document.write(currday.getFullYear()+"年"+currday.getMonth()+"月"+currday.getDay()+"日"+" "+week[currday.getDay()]);
//成绩是一长窜的字符串不好处理，找规律后分割放到数组里更好操作哦
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 arr=scoreStr.split(";")
var sum = 0;
for(var i=0;i<scoreStr.length;i++)
{
sum = sum+parseInt(arr[i].split(":")[1]);
}
document.write(sum+"<br/>");
//从数组中将成绩撮出来，然后求和取整，并输出。
document.write("班级总分"+sum);
</script>
</head>
<body>
</body>
</html>
