打印出都是女生的姓名var infos=[<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"]]; //第一步把之前的數據寫成一個數組的形式,定義變量為 infos for(var i=0;i<infos.length;i++){ if(infos[i][3]=='大一'&&infos[i][1]=='女'){ document.write(infos[i][0]+"<br/>");   } }這個什么i,infos[i][3]怎么去理解？