//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"]]

 for(var i = 0;i < infos.length;i++){

         var demo1=[];

         demo1=infos[i]

 //第一次筛选，找出都是大一的信息

 //第二次筛选，找出都是女生的信息

     for(var j = 0;j < demo1.length;j++ ){

        if(demo1[j]=="大一"&&demo1[j]=="女" ){

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

        }

     }

 }