请问求和的时候为嘛输出是NaN??

var tddate = new Date();

document.write(tddate);

var week=['星期天','星期一','星期二','星期三','星期四','星期五','星期六'];

var weekend=tddate.getDay(); 

document.write(week[weekend]+'<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 list = scoreStr.split(';');

var sum = 0;

var score = new Array();

for(var i=0;i<list.length;i++)

{ 

    score[i]=list[i].substr(7);

    sum=sum+parseInt('score[i]',10);

}