📄 17.10.htm
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>Better Form Validation</title>
<meta http-equiv="content-type" content="text/html; charset=gb2312">
<script type="text/javascript">
<!--
// 定义空白字符
var whitespace = " \t\n\r";
function isEmpty(s)
{
var i;
if((s == null) || (s.length == 0))
return true;
// Search string looking for characters that are not whitespace
for (i = 0; i < s.length; i++)
{
var c = s.charAt(i);
if (whitespace.indexOf(c) == -1)
return false;
}
// At this point all characters are whitespace.
return true;
}
function validate()
{
if (isEmpty(document.myform.username.value))
{
alert("Error: Username is required.");
document.myform.username.focus();
return false;
}
if (isEmpty(document.myform.userpass.value))
{
alert("Error: Non-empty password required.");
document.myform.userpass.focus();
return false;
}
return true;
}
//-->
</script>
</head>
<body>
<center><h1>改进的表单验证</h1>
提交前必须输入内容，但不可是空格。返回后，出错的表单域会获得焦点。</center>
<form name="myform" id="myform" method="get"
action="http://www.javascriptref.com"
onsubmit="return validate();">
Username:
<input type="text" name="username" id="username"
size="30" maxlength="60">
<br>
Password:
<input type="password" name="userpass" id="userpass"
size="8" maxlength="8">
<p>
<input type="submit" value="提 交">
</form>
</body>
</html>
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