How can i pass NULL value in ajax jquery call?

Is there any way to handle null value when doing Ajax Call?

 $.ajax({
            type: "POST",
            url: "Login.aspx/SaveFacebookAutoSignUp",
            data: "{ 'Name':'" + rows[0].name + "', 'EmailId': '" + rows[0].email + "'}",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (msg) {
                alert("You have successfully sign in.");

            }
        });

This is saving "null" value in my DB for EmailId when it is not fetch from other page?

I want to save "NULL" (DB default NULL allow) in DB when it is not having any value?

What is the way to do so?