JavaScript提供了一种在将表单数据发送到Web服务器之前在客户端计算机上对其进行验证的方法。
基本表单验证包括要检查的表单，以确保填写了所有必填字段。只需要循环遍历表单中的每个字段并检查数据即可。
您可以尝试运行以下代码以在JavaScript中实现基本表单验证-
<html>
<head>
<title>Form Validation</title>
<script>
//表单验证
function validate(){
if( document.myForm.Name.value == "" ) {
alert( "请提供您的名字！" );
document.myForm.Name.focus() ;
return false;
}
if( document.myForm.EMail.value == "" ){
alert( "请提供您的电子邮件！" );
document.myForm.EMail.focus() ;
return false;
}
if( document.myForm.Zip.value == "" ||
isNaN( document.myForm.Zip.value ) ||
document.myForm.Zip.value.length != 5 )
{
alert( "Please provide a zip in the format #####." );
document.myForm.Zip.focus() ;
return false;
}
if( document.myForm.Country.value == "-1" ){
alert( "请提供您的国家！" );
return false;
}
return( true );
}
</script>
</head>
<body>
<form action="/cgi-bin/test.cgi" name="myForm" onsubmit="return(validate());">
<table cellspacing = "2" cellpadding = "2" border = "1">
<tr>
<td align = "right">Name</td>
<td><input type = "text" name = "Name" /></td>
</tr>
<tr>
<td align = "right">EMail</td>
<td><input type = "text" name = "EMail" /></td>
</tr>
<tr>
<td align = "right">Zip Code</td>
<td><input type = "text" name = "Zip" /></td>
</tr>
<tr>
<td align = "right">Country</td>
<td>
<select name = "Country">
<option value = "-1" selected>[choose yours]</option>
<option value = "1">USA</option>
<option value = "2">UK</option>
<option value = "3">INDIA</option>
</select>
</td>
</tr>
<tr>
<td align = "right"></td>
<td><input type = "submit" value = "Submit" /></td>
</tr>
</table>
</form>
</body>
</html>