大神帮我看一下子！！！语法有问题吗？

var infos=new Array();

 //第一步把之前的数据写成一个数组的形式,定义变量为 infos

 infos=[["小A","女",21,"大一"],["小B","男",23,"大三"],["小C","男",24,"大四"],["小D","女",21,"大一"],["小E","女",22,"大四"],["小F","男",21,"大一"],["小G","女",22,"大二"],["小H","女",20,"大三"],["小I","女",20,"大一"],["小J","男",20,"大三"]];

for(var i=0;i<=9;i++){

    infos[i]=new Array();

    for(var j=0;j<=3;j++){

        infos[i][j]=new Array();

        if(infos[i][3]=="大一"){

            document.write(infos[i]+"<br>");

        }

        else

    }   

}