输出不了？

var mydate=new Date();

var dateToday=mydate.getFullYear()+"年"+mydate.getMonth()+'月'+mydate.getDate()+'日';

var myweekday=new Date();

var weekday=['Sunday','Monday','Tuesday','Weekday','Thursday','Friday','Saturday'];

document.write(dateToday.concat(weekday[myweekday.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 everyscore=scoreStr.split(';'); //此时every是一个数组。

// document.write(everyscore+"<br/>");

var sum=0;

for(i=0;i<=everyscore.length;i++){

var index=everyscore[i].indexOf(':')

var everynum=parseInt(everyscore[i].substr(index+1,2) );

// document.write(everynum+'&nbsp');

sum=sum+everynum;

}

document.write(sum);

还有，为什么参代里会给平均数赋值0，直接var av =sum/everyscore.length;不可以吗？