Javascript验证用户名长度
[英]Javascript Validating username Length
问题描述
I am trying to validate my username field and check if the username contains atleast 6 letters, if not then i show a pop up window indicating the same. 
我正在尝试验证我的用户名字段并检查用户名是否包含至少6个字母，如果没有，那么我会显示一个弹出窗口，指示相同。 But the alert command does not seem to work. 但是警报命令似乎不起作用。
Following is the code: 以下是代码：
<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>
2 个解决方案
解决方案1
3 已采纳 2015-11-17 20:45:35
You are trying to use the name element attribute as the id, which creates a global window property. 您正在尝试使用name元素属性作为id，这将创建一个全局窗口属性。 Name does not do that however, you can use. 名称不会这样做，但您可以使用。 You also aren't getting the value, you are trying to get the length on the element. 您也没有获得该值，您正试图获得该元素的长度。
document.getElementsByName('username1')[0].value
解决方案2
0 2015-11-17 21:18:39
Answer: I tried it this way it worked: 答：我尝试过这种方式：
<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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