<!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">
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",];
document.write(mydate.getFullYear()+"年"+parseFloat(mydate.getMonth()+1)+"月"+mydate.getDate()+"日 "+weekday[mydate.getDay()]+"<br>");
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 score1=new Array;
var score2=new Array;
var sum;
score1=scoreStr.split(";");
for(var i=0;i<score1.length;i++){
document.write(score1[i]+"<br>")
score2=score1[i].split("");
var a=score2[3]+score2[4];
document.write(a+"<br>")
sum=sum+parseInt(a);
}
sum=Math.round(sum/10);
document.write(sum);
</script>
</head>
<body>
</body>
</html>楼上正解,因为你只声明额sum,但是未设置初始值,默认为undefined,undefined/10是nan,math.floor后,还是nan.
给sum一个初始值0即可。