Unable to addClass using Javascript

Question

I would like to style all the empty textboxes,by adding a class on validation (ie on Submit), but my code isn't working. Not sure if its the script or the customvalidator. I only want to use JS. If I say

target.style.border="1px solid red";

its working though. Just unable to add the class.

JS:

<link href="StyleSheet.css" rel="stylesheet" type="text/css" />
<script type="text/javascript">
 function validateTextBox(sender, args) {
        var target = document.getElementById(sender.controltovalidate);
        var is_valid = target.value != "";
        if (is_valid) {
            target.removeClass("validate");
        }
        else {
            target.addClass("validate");
        }
        args.IsValid = is_valid;
    } 
</script>      

ASPX:

 <asp:TextBox ID="txtSurname" runat="server"></asp:TextBox>
 <asp:CustomValidator ID = "CustomValidator1" runat="server" 
 ControlToValidate="txtSurname" ValidateEmptyText="true" 
 ClientValidationFunction="validateTextBox"
 ></asp:CustomValidator>

CSS:

 .validate
 {
   border:2px solid red;
 }

Answer 1

document.getElementById returns a DOM element, which does not have addClass or removeClass APIs.

see: Element

To apply class, try (putting the idea, please tweak according to exact business logic):

target.className = target.className + " validate"

If we go with raw JS, we have to write raw code and forget luxuries of addClass or removeClass :-) To remove class, see this answer: Remove class using javascript

Answer 2

try this...

function validateTextBox(sender, args) {
        var target = document.getElementById(sender.controltovalidate.ClientID);
        if (target.value != "") {
            target.removeClass("validate");
        }
        else {
            target.addClass("validate");
        }
        args.IsValid = "";
    }  

Answer 3

Try this. Simple way .

function validateTextBox() {
        var target = document.getElementById("#<%= txtSurname.ClientID %>");
        **var is_valid = target.value;**
        **if (is_valid!="") {**
            target.removeClass("validate");
              **return true;**
        }
        else {
            target.addClass("validate");
            **return false**
        }

    } 

ASPX:

 <asp:TextBox ID="txtSurname" runat="server"></asp:TextBox>
 <asp:CustomValidator ID = "CustomValidator1" runat="server" 
 ControlToValidate="txtSurname" ValidateEmptyText="true" 
 ClientValidationFunction=**"Javascript:return validateTextBox()"**
 ></asp:CustomValidator>

Answer 4

Maybe you would like to use jquery validation plugin ? This is widely used plugin.

<asp:TextBox ID="txtSurname" runat="server" CssClass="toValidate"></asp:TextBox>

jQuery(function() {
    // You can specify some validation options here but not rules and messages
    jQuery('form').validate(); 
    // Add a custom class to your name mangled input and add rules like this
    jQuery('.toValidate').rules('add', { 
        required: true
    });
});

This code should check if textbox are empty before form submition.

Answer 5

change var target = document.getElementById(sender.controltovalidate.ClientID);

to: var target = document.getElementById(sender.ClientID);