E-mail validation in javascript

<script type="text/javascript">
           function fun_CheckEmailID(obj) 
           {
               var email_Value = Trim(obj.value);

               if (email_Value != "") 
               {
                   return Email_Single_NonMand(obj);
               }
               else 
               {
                   return true;
               }


           }

function Email_Single_NonMand(objval) 
{
    var emailfilter = /^\w+[\+\.\w-]*@([\w-]+\.)*\w+[\w-]*\.([a-z]{2,4}|\d+)$/i
    var objval1 = Trim(objval.value);
    var returnval = emailfilter.test(objval1);
    if (returnval == false)
     {
        alert("Please enter a valid email address.")
        document.getElementById(objval.id).value = "";
        return false;
     }
}
    
    </script>

 <asp:TextBox ID="txt_email" runat="server"  MaxLength="50"   onblur="return fun_CheckEmailID(this);">  </asp:TextBox>