                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript进阶篇

求问为什么均分是nan

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<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 myyear=mydate.getFullYear();
var weekend=new Array();
weekend=["星期日","星期一","星期二","星期三","星期四","星期五","星期六"];
var myday=mydate.getDay();
var mymonth=mydate.getMonth();
var yuefen=new Array();
yuefen=["一月","二月","三月","四月","五月","六月","七月","八月","九月","十月","十一月","十二月"];

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 sum=0;
var score=new Array();
for(var i=0;i<=9;i++)
{
score[i]=scoreStr.substr(3*(i+1),2);
sum += parseInt(score[i]);
}
document.write(myyear+"年"+yuefen[mymonth]+weekend[myday]+"--班级总分为:"+sum)
//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

//从数组中将成绩撮出来，然后求和取整，并输出。

</script>
</head>
<body>
</body>
</html