為什么不輸出呢？求救
?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"]
??????????????????????????????????? ];
?
?//第一次篩選，找出都是大一的信息
?var arr=[];
?n = 0;
?for (i=0;i<infos.length;i++){
?if （infos[i][3]=="大一"）{
???? arr[n]=infos[i]
???? }
?? ?
? document.write("大一學生："+arr[n]);
? n=n+1;
?}
?document.write("大一人數: "+arr.length+"<br/>");
?//第二次篩選，找出都是女生的信息
?
?for (i=0;i<arr.length;i++){
?if? (arr[i][1]=="女"){
???? docuemnt.write("大一女生："+arr[i][0]);
?}
?}
2016-10-18
兩個if可以直接在for循環里判斷完成，你的代碼有些冗余了。我復制你的代碼，?if （infos[i][3]=="大一"）這句話的括號是中文的，你看看。。。
2016-10-18
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title> 速度加快立法角度思考了 </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"]
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ]; ?
?var arr=[];
?var n = 0;
?for (i=0;i<infos.length;i++){
?if (infos[i][3]=="大一"){????????????????????????????????????????????????//你這（）有錯
? ? ?arr[n]=infos[i];
? ? ?
? ? ?document.write("大一學生："+arr[n]);????????????????????//你這邏輯錯誤
? ? ?n=n+1;
? ? ?} ?
?}
?document.write("大一人數: "+arr.length+"<br/>");
?//第二次篩選，找出都是女生的信息
?
?for (i=0;i<arr.length;i++){
?if ?(arr[i][1]=="女"){
? ? ?document.write("大一女生："+arr[i][0]);????????????????//你這拼寫錯誤
?}
?}
</script> ??
</head>
<body>
</body>
</html>
2016-10-18
你的問題可以復制到電腦上的軟件里運行下，好找出問題，代碼中有幾個問題：
if 后面是中文的括號
最后一個 document ?單詞寫錯了
document.write("大一學生："+arr[n]);
? n=n+1;
這兩行改寫至 if 里面
你可以試下。