本意是調用JavaScript定義的validate方法判斷多選框中是否沒有任何被選中的框,若是,則不跳轉,並彈出對話框提醒
源代碼如下
html界面
<%@ page language="java" contentType="text/html;charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<script type="text/javascript"src="../js/Option_Check.js"></script>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<formaction="Success.jsp" onSubmit="validate(this)">
<inputtype="checkbox" name="check" value="badman"/><b>badman</b>
<inputtype="checkbox" name="check" value="superman"/><b>superman</b>
<inputTYPE="submit" value="ok" />
</form>
</body>
</html>
js代碼
function validate(f){
var field=f.check;
var i=0;
for(;i<field.length;i++){
if(field[i].checked){
return true;
}
}
alert("未選擇任何一項");
return false;
}
結果能彈出一個對話框提示“未選擇任何一項”,但是點擊確定後依舊轉移到Success.jsp界面
錯誤在於調用的方式錯了(onSubmit="validate(this)")
受Java的影響,調用有返回數據的方法直接調用即可,但是JavaScript中需要加上return關鍵字才能得到函數返回的值
正確的html語句
<%@ page language="java" contentType="text/html;charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<script type="text/javascript"src="../js/Option_Check.js"></script>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<formaction="Success.jsp" onSubmit="return validate(this)">
<inputtype="checkbox" name="check" value="badman"/><b>badman</b>
<inputtype="checkbox" name="check" value="superman"/><b>superman</b>
<inputTYPE="submit" value="ok" />
</form>
</body>
</html>