/* Code Behind*/

<code>protected string iTabId

        {

            get

            {

                object setting = UserModuleBase.GetSetting(base.PortalId, "Redirect_AfterLogin");

                if (setting != null)

                    return setting.ToString();

                return PortalSettings.HomeTabId.ToString();

            }

        }

ASCX Controls

<script type="text/javascript">

    var redTabid =  <%= "'" + this.iTabId  + "'" %>;

</script>

</code>

You can change your reuired tabid on Property on code-behind