Validation In Blog Comment Form

To Add validation using java script need to create function and callback to replay button

function fnCommentSubmit()
    {
<?php if (!is_user_logged_in()) { ?>
            document.getElementById("a_name").innerHTML = "";
            document.getElementById("a_email").innerHTML = "";
<?php } ?>
        document.getElementById("a_msg").innerHTML = "";
        var flag = 0;
        var objName = document.getElementById("author");
        var objEmail = document.getElementById("email");
        var objMessage = document.getElementById("comment");
<?php if (!is_user_logged_in()) { ?>
            if (objName != null)
            {
                var regExp = /^[a-zA-Z\s]+$/;
                var checkName = regExp.test(objName.value.trim());
                if (objName.value.trim() == "")
                {
                    document.getElementById("a_name").innerHTML = "Name is Required";
                    flag = 1;
                }
                else if (checkName == false)
                {
                    document.getElementById("a_name").innerHTML = "Please Enter a Correct Value";
                    flag = 1;
                }
            }
            if (objEmail != null)
            {
                var regExp = /^[a-zA-Z0-9._+%-]+@[a-zA-Z0-9._]+\.[a-zA-Z]+$/;
                var check = regExp.test(objEmail.value.trim());
                if (objEmail.value.trim() == "")
                {
                    document.getElementById("a_email").innerHTML = "Email is Required";
                    flag = 1;
                }
                else if (check == false) {
                    document.getElementById("a_email").innerHTML = "Please Enter a Correct Email Address";
                    flag = 1;
                }
            }
<?php } ?>
        if (objMessage != null)
        {
            if (objMessage.value.trim() == "")
            {
                document.getElementById("a_msg").innerHTML = "Message is Required";
                flag = 1;
            }
        }
        if (flag == 1)
        {
            return false;
        }
        else
        {
            return true;
        }
    }

Now return function of submit button of comment form