請(qǐng)問下按照下面代碼寫為什么會(huì)出錯(cuò)?。?/h1>
<!DOCTYPE??HTML>
<html?>
<head>
<meta?http-equiv="Content-Type"?content="text/html;?charset=utf-8"?/>
<title>流程控制語(yǔ)句</title>
<script?type="text/javascript">
?//第一步把之前的數(shù)據(jù)寫成一個(gè)數(shù)組的形式,定義變量為?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"]];
?
?//第一次篩選，找出都是大一的信息
?var?infos2=new?Array(5);
?var?a=0;
?var?b=0;
??for(var?i=0;i<10;i++){
??????
??????if(infos[i][3]=="大一"){
??????????
??????????infos2[a]=infos[i];
??????????a++;
??????}
??}
?//第二次篩選，找出都是女生的信息
??var?infos3=new?Array(3);
??for(var?j=0;j<infos2.length;j++){
??????
??????if(infos2[j][1]=="女"){
??????????infos3[b]=infos2[j];
??????????b++;
??????????
??????}
??}
??document.write(infos3);
??
</script>
</head>
<body>
</body>
</html>我試了下如果最后一個(gè)if語(yǔ)句中換成document.write(infos2[j])的話是對(duì)的，不知道為什么按上面所寫的會(huì)出錯(cuò);
<!DOCTYPE??HTML>
<html?>
<head>
<meta?http-equiv="Content-Type"?content="text/html;?charset=utf-8"?/>
<title>流程控制語(yǔ)句</title>
<script?type="text/javascript">
?//第一步把之前的數(shù)據(jù)寫成一個(gè)數(shù)組的形式,定義變量為?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"]];
?
?//第一次篩選，找出都是大一的信息
?var?infos2=new?Array(5);
?var?a=0;
?var?b=0;
??for(var?i=0;i<10;i++){
??????
??????if(infos[i][3]=="大一"){
??????????
??????????infos2[a]=infos[i];
??????????a++;
??????}
??}
?//第二次篩選，找出都是女生的信息
??var?infos3=new?Array(3);
??for(var?j=0;j<infos2.length;j++){
??????
??????if(infos2[j][1]=="女"){
??????????infos3[b]=infos2[j];
??????????b++;
??????????
??????}
??}
??document.write(infos3);
??
</script>
</head>
<body>
</body>
</html>我試了下如果最后一個(gè)if語(yǔ)句中換成document.write(infos2[j])的話是對(duì)的，不知道為什么按上面所寫的會(huì)出錯(cuò);
2017-08-29
有點(diǎn)雜耍了。。。其實(shí)很多不用寫的。。。你這出現(xiàn)的問題是數(shù)組infos2給多了個(gè)位置，在for循環(huán)的時(shí)候，當(dāng)他循環(huán)到空值時(shí)會(huì)誤以為你沒有定義。。。還有哥們，你是學(xué)JAVA過來學(xué)JS的吧？不然一般人不會(huì)先定義數(shù)組的大小。。。