Client Side Validation with JavaScript in ASP.NET

[DOTNETPRO]

This simple program will guide how to do client side validation of Form
in JavaScript.

In this just make a form as follows:

Name : <asp:TextBox ID="txtName" />
Email : <asp:TextBox ID="txtEmail" />
Web URL : <asp:TextBox ID="txtWebUrl" />
Zip : <asp:TextBox ID="txtZip" />
<asp:Button ID="btnSubmit" OnClientClick=" return validate()"
runat="server" Text="Submit" />

Now on the source code of this form in script tag write the following
code:

<script language="javascript" type="text/javascript">
function validate()
{
if (document.getElementById("<%=txtName.ClientID%>").value=="")
{
alert("Name Feild can not be blank");

document.getElementById("<%=txtName.ClientID%>").focus();
return false;
}
if(document.getElementById("<%=txtEmail.ClientID %>").value=="")
{
alert("Email id can not be blank");
document.getElementById("<%=txtEmail.ClientID
%>").focus();
return false;
}
var emailPat =
/^(\".*\"|[A-Za-z]\w*)@(\[\d{1,3}(\.\d{1,3}){3}]|[A-Za-z]\w*(\.[A-Za-z]\w*)+)$/;
var emailid=document.getElementById("<%=txtEmail.ClientID
%>").value;
var matchArray = emailid.match(emailPat);
if (matchArray == null)
{
alert("Your email address seems incorrect. Please try
again.");
document.getElementById("<%=txtEmail.ClientID
%>").focus();
return false;
}
if(document.getElementById("<%=txtWebURL.ClientID %>").value=="")
{
alert("Web URL can not be blank");
document.getElementById("<%=txtWebURL.ClientID
%>").value="http://"
document.getElementById("<%=txtWebURL.ClientID
%>").focus();
return false;
}
var Url="^[A-Za-z]+://[A-Za-z0-9-_]+\\.[A-Za-z0-9-_%&\?\/.=]+$"
var
tempURL=document.getElementById("<%=txtWebURL.ClientID%>").value;
var matchURL=tempURL.match(Url);
if(matchURL==null)
{
alert("Web URL does not look valid");
document.getElementById("<%=txtWebURL.ClientID
%>").focus();
return false;
}
if (document.getElementById("<%=txtZIP.ClientID%>").value=="")
{
alert("Zip Code is not valid");
document.getElementById("<%=txtZIP.ClientID%>").focus();
return false;
}
var digits="0123456789";
var temp;
for (var i=0;i<document.getElementById("<%=txtZIP.ClientID
%>").value.length;i++)
{

temp=document.getElementById("<%=txtZIP.ClientID%>").value.substring(i,i+1);
if (digits.indexOf(temp)==-1)
{
alert("Please enter correct zip code");

document.getElementById("<%=txtZIP.ClientID%>").focus();
return false;
}
}
return true;
}
</script>

And in code behind file just write the below code.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Load
btnSubmit.Attributes.Add("onclick", "return validate()")
End Sub

Now you will get a form with proper validation.