比如这个第二步怎么筛选？
<!DOCTYPE HTML>
<html >
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>流程控制语句</title>
<script type="text/javascript">
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"]];
//第一步把之前的数据写成一个数组的形式,定义变量为 infos
var temp = new Array();//需要一个数组来存储选择出来的的信息
var num = 0;
for(var i=0;i<infos.length;i++){
if(infos[i][3] =='大一')
{
document.write(infos[i]);//验证我们是否选择出了全部大一学生
temp[num] = infos[i];//存储到temp中
num++;//为下次存储做准备
}
}
//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
</script>
</head>
<body>
</body>
</html>infos[0]是第一行，值为["小A","女",21,"大一"]。
infos[0][1]是第一行第二列，值为"女"。