本人代码如下
<!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 mon = myDate.getMonth() + 1;
var dat = myDate.getDate();
var weekDay = myDate.getDay();
var week;
switch(weekDay){
case 0:
week = "一";
break;
case 1:
week = "二";
break;
case 2:
week = "三";
break;
case 3:
week = "四";
break;
case 4:
week = "五";
break;
case 5:
week = "六";
break;
case 6:
week = "日";
break;
}
//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 grade = scoreStr.split(";");
//document.write(grade);
//从数组中将成绩撮出来，然后求和取整，并输出。
var myGrade = new Array();
var sum = 0;
for(var i = 0; i < grade.length; i++){
//document.write(grade[i].slice(3,5) + "<br>");
myGrade[i] = grade[i].slice(3,5);
sum = parseInt(myGrade[i]) + sum;
}
var verage = sum/grade.length;
document.write(year + "年" + mon + "月" + dat + "日 星期" + week + "--班级平均分为:" + verage + "<br>");
</script>
</head>
<body>
</body>
</html>
