jquery - assign a text to a textbox when checkbox is checked by client

   $('#<%= CheckBox1.ClientID %>').click(function ()
        {
           

            if (this.checked)
            {
                $('#<%= firstnamedrivertxt.ClientID %>').val($('#<%= firstnametxt.ClientID %>').val());
            }
            else
            {
                $('#<%= firstnamedrivertxt.ClientID %>').val(null);
            }
        });