讲真写出来了但是为什么这里i和j的值会符合筛选条件啊  值是怎么来的

 var 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"]];

 var i,j=0;

 //第一次筛选，找出都是大一的信息

 for(i=0;i<10;i++){

     if(infos[i][3]=="大一"){

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

     }

 }

  document.write("<br/>")

 //第二次筛选，找出都是女生的信息

   for(j=0;j<infos.length;j++){

     if(infos[j][1]=="女"){

         document.write(infos[j]+"<br/>")

     }

 }