//第一步把之前的数据写成一个数组的形式,定义变量为 infos

  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"]];

 //第一次筛选，找出都是大一的信息

  document.write(infos[0][1]+"<br>")

 for(var i=0;i<infos.length;i++){

    if(infos[i][1]=="女" && infos[i][3]=="大一"){

          document.write(infos[i][0]+"<br>")    }

  }

  这样有错吗？