有點問題，求教
<!DOCTYPE? HTML>
<html >
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>系好安全帶,準備啟航</title>
<script type="text/javascript">
? //通過javascript的日期對象來得到當前的日期，并輸出。
? 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()]
????? );
? //成績是一長竄的字符串不好處理，找規(guī)律后分割放到數(shù)組里更好操作哦
? var sorceStr = "小明:87;小花:81;小紅:97;小天:76;小張:74;小小:94;小西:90;小伍:76;小迪:64;小曼:76";
? var sourceArr = sorceStr.split(";");
? //document.write(sourceArr);//test
?? //從數(shù)組中將成績撮出來，然后求和取整，并輸出。
?? var score = new Array();
?? var sum = 0;
?? for (var i = 0; i < sourceArr.length; i ++) {
?????? sum += parseInt(sourceArr[i].substr(sourceArr[i].indexOf(":")+1));
?????? //document.write("<br>" + sum);//test
?? }
?? document.write("--班級總分為:" + sum);
?? document.write(",班級平均分為(保留整數(shù)):" + Math.round(sum/sourceArr.length))
</script>
</head>
<body>
</body>
可以解釋一下從最后中文注釋到for語句那里的意思嗎，我看不懂
2016-11-28
覺得這樣比較簡潔：
?var mydayte=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(mydayte.getFullYear()+"年"+(mydayte.getMonth()+1)+"月"+mydayte.getDate()+"日"+" ?"+weekday[mydayte.getDay()]+" ?--班級總分為："+sum+" ?平均分為:"+sum/scoreStr.length);
? var scoreStr =["小明:87","小花:81","小紅:97","小天:76","小張:74","小小:94","小西:90","小伍:76","小迪:64","小曼:76"];
? ? var sum=0;
? ? for(var i=0;i<scoreStr.length;i++){
? ? ? sum+=parseInt(scoreStr[i].substr(scoreStr[i].indexOf(":")+1));
? }
2016-11-06
? var sorceStr = "小明:87;小花:81;小紅:97;小天:76;小張:74;小小:94;小西:90;小伍:76;小迪:64;小曼:76";
? var sourceArr = sorceStr.split(";");//把長的字符串分成（小明：87）這種短的字符串
? ?var score = new Array();//建一個數(shù)組，（小明：87）是score【0】
?? var sum = 0;
?? for (var i = 0; i < sourceArr.length; i ++) {
?????? sum += parseInt(sourceArr[i].substr(sourceArr[i].indexOf(":")+1));//sourceArr[i].indexOf（“：”）+1求出score[0]的 數(shù)值為2+1=3，(sourceArr[0].substr（3）?求出 87