[英]Why don't jQuery/JavaScript (classname or id).value.length work when validating username?
[英]Javascript Validating username Length
我正在嘗試驗證我的用戶名字段並檢查用戶名是否包含至少6個字母,如果沒有,那么我會顯示一個彈出窗口,指示相同。 但是警報命令似乎不起作用。
以下是代碼:
<html>
<head>
<title> Webpage </title>
</head>
<script language="Javascript">
function validate()
{
if (username1.length < 6)
{
alert("Username must be atleast 6 charactrs long, Please Try Again");
}
}
</script>
<body>
<form>
<center>
<fieldset>
<table cellspacin="5" cellpadding="5" border="0">
<tr>
<td>Username: </td>
<td align="left"><input type=="text" name="username1" maxlength="20" size="20">
</td>
</tr>
<tr>
<td> Password: </td>
<td align = "left"> <input type="text" name="password" maxlength="20" size="20">
</td>
</tr>
<tr>
<td> Please confirm your password: </td>
<td align = "left"> <input type="text" name="password1" maxlength="20" size="20">
</td>
</tr>
<tr>
<td align="center"><input type="submit" value="Log in" onClick="validate()">
</td>
</tr>
</fieldset>
</table>
</center>
</form>
</body>
</html>
您正在嘗試使用name元素屬性作為id,這將創建一個全局窗口屬性。 名稱不會這樣做,但您可以使用。 您也沒有獲得該值,您正試圖獲得該元素的長度。
document.getElementsByName('username1')[0].value
答:我嘗試過這種方式:
<html>
<head>
<title> Webpage </title>
</head>
<script language="Javascript">
function validate()
{
username2 =form1.username1.value
if (username2.length < 6)
{
alert("Username must be atleast 6 charactrs long, Please Try Again");
}
}
</script>
<body>
<form name="form1">
<center>
<fieldset>
<table cellspacin="5" cellpadding="5" border="0">
<tr>
<td>Username: </td>
<td align="left"><input type=="text" name="username1" maxlength="20" size="20">
</td>
</tr>
<tr>
<td> Password: </td>
<td align = "left"> <input type="text" name="password" maxlength="20" size="20">
</td>
</tr>
<tr>
<td> Please confirm your password: </td>
<td align = "left"> <input type="text" name="password1" maxlength="20" size="20">
</td>
</tr>
<tr>
<td align="center"><input type="submit" value="Log in" onClick="validate()">
</td>
</tr>
</fieldset>
</table>
</center>
</form>
</body>
</html>
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