大神帮忙看一下，为什么最后不能输出总分数sum值，多谢了
<!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 currentDate = 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(
currentDate.getFullYear()+"年"+
( currentDate.getMonth()+1+"月")+
currentDate.getDate()+"日"+
weekday[currentDate.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 sourceArr = scoreStr.split(";");
//document.write(sourceArr);
var sum = 0;
for(var i=0;i<=sourceArr.length;i++){
sum+=parseInt(sourceArr[i].substr(sourceArr[i].indexOf(":")+1));
document.write("<br>"+sum);
}
document.write(sum);
</script>
</head>
<body>
</body>
</html>
