终于弄出来了，应该没错了
<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 weekday=["星期日","星期一","星期二","星期三","星期四","星期五","星期六"];
var b=mydate.getDay();
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 fg=scoreStr.split(";");
var sum=0,pjf=0;
for(var i=0;i<fg.length;i++){
sum=sum+parseInt(fg[i].substring(3,5));
pjf=Math.floor(sum/parseInt(fg.length));
}
document.write(mydate.getFullYear()+"年"+mydate.getMonth()+"月"+mydate.getDate()+"日"+" "+weekday[b]+" "+"班级总分："+sum+"<br>"+"平均分"+pjf);
</script>
</head>
<body>
</body>
</html>
