自己写了份正确答案（可参考）
<!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 mydate=new Date();
var year=mydate.getFullYear();
var month=mydate.getMonth()+1;
var date=mydate.getDate();
var num=mydate.getDay();
var weekday=["星期日","星期一","星期二","星期三","星期四","星期五","星期六"];
var formatday=year+"年"+month+"月"+date+"日"+weekday[num];
document.write(formatday+"<br/>");
//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 persons = scoreStr.split("\;");
var score=0;
for (var i = 0; i < persons.length ; i++)
{
score = score + parseInt( persons[i].split("\:")[1] );
document.write(persons[i].split("\:")+"</br>")
}
//从数组中将成绩撮出来，然后求和取整，并输出。
document.write("总分"+score+"</br>")
document.write("平均分"+Math.round(score/(persons.length+1)))
</script>
</head>
<body>
</body>
</html>
