成功啦，欢迎大家参考提问
<!DOCTYPE HTML>
<html >
<head>
<meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,minimum-scale=1,user-scalable=no">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>取值</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 weekday=["星期日","星期一","星期二","星期三","星期四","星期五","星期六"];
var year=mydate.getFullYear();
var month=mydate.getMonth();
var day=mydate.getDate();
document.write(year+"年"+month+"月"+day+"日"+ ","+weekday[mydate.getDay()]+"<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 num=scoreStr.split(";");
var sum=0;
for(var i=0;i<num.length;i++){
sum+=parseInt(num[i].substring(3));
}
//从数组中将成绩撮出来，然后求和取整，并输出。
document.write(parseInt(sum/num.length));
</script>
</head>
<body>
</body>
</html>
